Geometry Proof Statements

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Questions and Answers

Consider two triangles, $\triangle ABC$ and $\triangle DEF$, where $\overline{AB} \cong \overline{DE}$ and $\overline{BC} \cong \overline{EF}$. Under what additional condition, invoking the most nuanced interpretation of geometric congruence, can it be definitively proven that $\triangle ABC \cong \triangle DEF$ by SAS, while accounting for potential elliptic or hyperbolic geometric spaces?

  • $\angle BAC \cong \angle EDF$, assuming Euclidean space.
  • The area of $\triangle ABC$ is equal to the area of $\triangle DEF$, confirming conservation of area under SAS congruence.
  • $\angle ACB \cong \angle DFE$, irrespective of the underlying geometric space.
  • $\angle ABC \cong \angle DEF$, with assurance that the curvature of the space approaches zero. (correct)

Considering the intricacies of geometric proofs, what subtle distinction differentiates the application of the Transitive Property of Equality from the Substitution Property of Equality, particularly when dealing with complex algebraic manipulations within geometric contexts?

  • The Transitive Property applies only to numerical equalities, whereas the Substitution Property is exclusively for variable expressions.
  • There is no practical difference; the properties are interchangeable in all mathematical contexts.
  • The Transitive Property is applicable in Euclidean geometry, whereas the Substitution Property is reserved for non-Euclidean geometries.
  • The Transitive Property necessitates a direct chain of equalities (a=b, b=c, thus a=c), while the Substitution Property allows for replacing a term with an equal term within a more complex expression, regardless of the direct chain. (correct)

Within the framework of advanced Euclidean geometry, if two lines are deemed 'perpendicular' predicated solely on the basis that they intersect at a 90-degree angle, what inherent limitation arises when attempting to extend this definition to three-dimensional space, especially concerning the definition of planes and their orthogonality?

  • The concept of 'perpendicularity' is intrinsically two-dimensional and cannot be extrapolated to higher dimensions.
  • Three-dimensional space requires angles to be measured in radians, making the 90-degree definition obsolete.
  • In three-dimensional space, lines intersecting at 90 degrees do not necessarily define a unique plane.
  • Defining perpendicularity solely by a 90-degree angle fails to account for skew lines in three-dimensional space. (correct)

Given that $\overleftrightarrow{JL}$ and $\overleftrightarrow{JK}$ form opposite rays sharing a common endpoint $J$ and creating a straight line, consider a scenario where measurements are taken with inherent instrument imprecision. If $m\angle LJK$ is determined to be $180.00001$ degrees, what is the most theoretically sound justification for still treating $\overleftrightarrow{JL}$ and $\overleftrightarrow{JK}$ as forming a straight line within the context of geometric proofs?

<p>Measurement inaccuracies are inherent, and as the measured angle lies within the margin of error, practical applications dictate classification as a straight line. (B)</p> Signup and view all the answers

In advanced geometric constructions, the Angle Addition Postulate typically relies on empirical observations. However, what underlying set-theoretic principle, when rigorously formalized, truly justifies the validity of this postulate when extended to include infinite sets of angles, or angles defined using transcendental functions?

<p>Lebesgue integration provides a means to define angle measures over continuous sets, enabling a measure-theoretic Angle Addition Postulate. (B)</p> Signup and view all the answers

Consider the rigorous axiomatic foundations of equality. Which of the following statements most precisely encapsulates the subtle distinction between the Reflexive Property of Equality ($a = a$) and the concept of identity ($a \equiv a$), particularly in the context of abstract algebra where elements may not possess inherent numerical values?

<p>The Reflexive Property is a statement about the equality of numerical values, whereas identity is a statement that an element is indistinguishable from itself under a specific mathematical operation. (A)</p> Signup and view all the answers

Given quadrilateral ABCD is a parallelogram, which of the following best describes, with the most advanced rigor, how the properties used to prove that ABCD is a parallelogram differ from the properties that are true because ABCD is a parallelogram?

<p>Properties used to prove ABCD is a parallelogram concern conditions that, when met, establish it <em>must</em> be a parallelogram. Properties that are true <em>because</em> ABCD is a parallelogram are logical consequences of that definition. (D)</p> Signup and view all the answers

Consider the intricacies of proving that two triangles are congruent using only rigid motions. What constitutes the most precise set-theoretic formalization of a 'rigid motion' that preserves distances, especially when examined in the context of non-Euclidean geometries such as hyperbolic space?

<p>A rigid motion is a transformation that induces a permutation on the set of points in a geometric space such that the metric tensor is invariant under the transformation. (D)</p> Signup and view all the answers

Given that $\overline{AB} \cong \overline{CD}$ and $\overline{CD} \cong \overline{AD}$, what deeper insight, beyond the direct application of the Symmetric Property of Congruence, is gleaned regarding the meta-mathematical relationship between the observer and the geometric entities when asserting $\overline{CD} \cong \overline{AD}$ from $\overline{AD} \cong \overline{CD}$?

<p>The Symmetric Property demonstrates the objectivity of congruence relations, invariant to the order in which entities are considered. (C)</p> Signup and view all the answers

Within the rigorous framework of axiomatic projective geometry, where parallelism is redefined and traditional Euclidean metrics are absent, how would you articulate the inherent limitations in employing Alternate Exterior Angles Theorem for establishing parallelism between two lines intersected by a transversal?

<p>The Alternate Exterior Angles Theorem relies on Euclidean axioms, which are fundamentally incompatible with the axioms of projective geometry. (C)</p> Signup and view all the answers

Within the context of non-Euclidean geometries such as hyperbolic geometry, what fundamental modification must be made to the Same-Side Interior Angles Postulate to accurately reflect the relationship between angles formed when two lines are intersected by a transversal, and the lines do not converge?

<p>The sum of the same-side interior angles must be strictly greater than 180 degrees. (C)</p> Signup and view all the answers

Let's consider the Converse of the Alternate Interior Angles Theorem. What modification(s) will render the Converse of the Alternate Interior Angles Theorem adaptable and valid within the system of spherical geometry, where traditional notions of parallelism are fundamentally challenged?

<p>The theorem can be adapted by relating &quot;congruent&quot; alternate interior angles to the geodesic curvature along the lines, accounting for surface curvature. (C)</p> Signup and view all the answers

In the context of hyperbolic geometry, where the Parallel Postulate does not hold, what nuanced adjustment is necessitated when applying the Converse of the Corresponding Angles Theorem to establish a specific relationship between two lines intersected by a transversal?

<p>Ensuring that ultra-parallel lines display corresponding angles approaching equality asymptotically at their points of greatest separation. (C)</p> Signup and view all the answers

When dealing with the Parallel Postulate in geometries beyond Euclidean space, what represents the most critical conceptual refinement necessary to understand geometrically spaces where, through a point $P$ not on a line $l$, there exist either no parallels or infinitely many parallels to $l$?

<p>Acknowledging that curvature radically alters linear and angular relationships, hence parallels diverge or converge. (A)</p> Signup and view all the answers

How does the introduction of infinitesimals into the continuum impact the conventional understanding of the Perpendicular Bisector Theorem, if at all?

<p>Infinitesimals refine understanding; theorems hold in limits, bisection is then approximate, not absolute. (B)</p> Signup and view all the answers

Assume we operate within a geometric framework lacking the Archimedean property. How does this theoretical violation influence the validity and applicability of the Perpendicular Bisector Theorem, particularly regarding the concept of equidistance?

<p>No point is equidistant to the segment endpoints. (D)</p> Signup and view all the answers

Within the nuances of synthetic geometry, to truly establish triangle congruence via ASA, which condition offers the most resistance to geometric spaces where Euclid’s axioms do not fully hold?

<p>Rigorous proof that triangles can be mapped one to one using only rigid motions. (C)</p> Signup and view all the answers

What is the core difference between establishing triangle similarity via AAA in traditional Euclidean space versus doing so on the surface of a sphere, where angle excess is integral?

<p>Congruence, not similarity, holds upon AAA's establishment in spherical contexts. (C)</p> Signup and view all the answers

Consider the case of proving triangle congruence using Side-Side-Side (SSS). What deep consideration must be at the forefront concerning metric tensor invariance to accommodate validity within non-Euclidean spaces exhibiting noticeable curvature?

<p>SSS should guarantee an invariant geodesic triangle construction. (D)</p> Signup and view all the answers

How might a non-Archimedean setting influence the Third Angles Theorem, particularly concerning situations involving infinitesimal or unlimited values for known angle measurements?

<p>Angle addition's behavior might demand specific constraints on non-Archimedean quantities. (C)</p> Signup and view all the answers

How does assuming an absolute, fixed background universe influence the application of the Hypotenuse-Leg (HL) Congruence Theorem in advanced geometrical constructions?

<p>HL use becomes simpler since transformations preserve distance. (D)</p> Signup and view all the answers

Let's examine Triangle Sum Theorem. If operating in a truly non-Euclidean, curved space, which adjustment to this basic theorem becomes essential for validity?

<p>Incorporating local space curvature impact in total angle measures becomes essential. (C)</p> Signup and view all the answers

What becomes the truly challenging aspect when assessing Isosceles Triangle Theorem's applicability in discrete geometrical spaces (where continuity isn't preserved)?

<p>Establishing congruency with noncontinuous lines requires unique treatment. (C)</p> Signup and view all the answers

What is the primary obstacle to directly applying the Converse of the Isosceles Triangle Theorem in constructive (intuitionistic) mathematics, where proofs must provide explicit constructions and cannot solely rely on the law of excluded middle?

<p>The inability, constructively, to guarantee the existence of an isosceles triangle given two equal angles without explicitly constructing it. (B)</p> Signup and view all the answers

How will the Triangle Inequality Theorem present unexpected complexities within settings characterized by fractal geometries, or those having Hausdorff dimensions not equal to integers?

<p>Notions of distance become scale-dependent. (C)</p> Signup and view all the answers

In a geometric space where any two points can be connected by infinitely many distinct geodesics, each possessing a differing length, what critical consideration arises when applying the Side-Angle Relationship in Triangles?

<p>A specific metric must define geodesics; relationships holds only for that choice. (A)</p> Signup and view all the answers

How might quantum entanglement principles force re-evaluation or redefine the Angle-Side Relationship in Triangles, where spatially separated attributes potentially correlate?

<p>Relationships hold conditioned through entangled probabilities. (C)</p> Signup and view all the answers

Given knowledge of the Circumcenter Theorem, how will our perception alter upon working within an elliptic geometry, rather than the more basic Euclidean structures?

<p>Perpendicular bisectors may not concur; triangles lack circumcircles. (C)</p> Signup and view all the answers

Within geometries refusing global notions (lacking translation or rotation symmetry), which inherent limitation arises upon applying theorems like the Incenter Theorem, related to angle bisectors meeting at a common location?

<p>The theorem has limited significance since no meaningful origin lies. (D)</p> Signup and view all the answers

What inherent constraint affects the application and interpretation of theorems concerning the concurrency of medians (namely Centroid Theorem), across non-orientable surfaces, such as the Klein bottle or Möbius strip?

<p>Defining midpoints is not globally consistent; medians show anomalous behavior. (D)</p> Signup and view all the answers

What must be seriously reconsidered regarding the classical interpretation for the Definition of Altitude (segment perpendicular from a vertex to the containing line), across spaces containing singularities, boundaries or other such exceptional structures?

<p>Perpendicularity or the &quot;containing line&quot; requires alternative constructions. (C)</p> Signup and view all the answers

How does the validity and utility of the Definition of Midsegment degrade as constructions approach those relying upon quantum geometrical frameworks, where spatial relationships inherently embody uncertainty?

<p>Defining midpoints necessitates probabilistic treatment; certainty degrades. (A)</p> Signup and view all the answers

Focusing upon parallelogram properties, how would you need to reinterpret the 2 pairs of // Sides condition upon adapting it to 4-dimensional (or higher) Minkowski space-time?

<p>2 pairs of // sides means constant velocity; // is reinterpreted. (C)</p> Signup and view all the answers

How will our conventional understanding of Rectangle diagonality alter greatly as working with curved space-times, most critically when nearing the event horizon of blackhole?

<p>Spacetime curvature causes distortions in lengths; diagonals seemingly differ. (C)</p> Signup and view all the answers

Imagine that conventional geometrical compass-and-straightedge tools are not viable. What theoretical implications arise regarding Kite properties during establishment using only quantum computational constructs relying upon superposition and entanglement?

<p>Kite distances become non-absolute; entanglement necessitates inherent uncertainty. (D)</p> Signup and view all the answers

What limitation surfaces in establishing Trapezoid properties, most notably parallelism relationships, in digital constructive settings (where geometric statements necessitate algorithmic, step-by-step construction) instead of pure deductive theorems?

<p>Establishing 'true' parallelism is limited; it's only approximation. (D)</p> Signup and view all the answers

If all points existed on a closed, infinitely differentiable manifold exhibiting rotational symmetry, what subtle implications might impact Arc Length applications, requiring re-examination?

<p>Endpoints can converge multiple times; Arc Length may relate to winding. (B)</p> Signup and view all the answers

Under what conditions will computations of area on the hyperbolic plane (constant negative curvature) render conventional Sector Area applications fundamentally ill-defined without significant adaptation?

<p>When sector is not infinitesimally small compared to Gaussian curvature scales. (C)</p> Signup and view all the answers

Imagine the universe underwent expansion obeying unusual non-commutative geometrical underpinnings. How will we have to reconsider the standard Surface Area theorems governing volume calculations, given we lose conventional commutativity?

<p>Non-commutative operators complicate integration deeply. (C)</p> Signup and view all the answers

With quantum entanglement principles strongly in play, how may we need to drastically reimagine traditional Geometric Probability concepts upon assigning probabilities to geometric outcomes from spatial correlations?

<p>Probabilities need revision for measurement effects. (D)</p> Signup and view all the answers

Flashcards

What is a right triangle?

A triangle with one right angle.

What is the definition of a line segment?

Through any two points there is exactly one line.

What is the Segment Addition Postulate?

If A, B, and C are collinear points and B is between A and C, then AB + BC = AC

What is the distance formula?

The distance between two points is calculated with: D = √((x₂ − x₁)² + (y₂ − y₁)²)

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What defines a midpoint?

If AC = CE, then point C is the midpoint.

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What is the midpoint formula?

The midpoint between two points is calculated with: M = ((x₁ + x₂)/2, (y₁ + y₂)/2)

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What is the definition of Angle Bisector?

If DB bisects ∠ABC, then m∠ABD = m∠DBC

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What is the symmetric property of equality?

If a=b, then b=a

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What is the transitive property of equality?

If a=b and b=c, then a=c

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What is a linear pair?

A pair of adjacent angles whose noncommon sides are opposite rays.

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What are opposite rays?

Two rays that start from a common point and go off in exactly opposite directions.

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What is a straight angle?

An angle that is equal to 180 degrees.

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What are perpendicular lines?

Two lines that meet at a 90 degree angle.

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When are angles supplementary?

If the sum of two angle measures is 180 degrees, they are supplementary.

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When are angles complementary?

If the sum of two angles is 90 degrees, they are complementary.

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What is the Linear Pair Theorem?

If two angles form a linear pair, they are supplementary and their measures add up to 180.

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What does 'congruent' mean?

Congruent means identical in shape and size.

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What are congruent figures?

Two plane figures are congruent if and only if one can be obtained from the other by a sequence of rigid motions (reflections, translations, rotations).

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What is CPCTC?

If two triangles are congruent, then every corresponding part is congruent to each other.

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What does the Vertical Angle Theorem state?

If two angles are vertical angles, then the angles are congruent.

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What is defined by Congruent Supplements Theorem?

If two angles are congruent, then their supplements are congruent.

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What defines the Congruent Complements Theorem?

If two angles are congruent, then their complements are congruent.

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What is the Alternate Exterior Angles Theorem?

If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles have the same measure.

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What is the Alternate Interior Angles Theorem?

If two parallel lines are cut by a transversal, then the pairs of alternate interior angles have the same measure.

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What is the Corresponding Angles Theorem?

If two parallel lines are cut by a transversal, then the pairs of corresponding angles have the same measure.

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What proves parallel lines with alternate exterior angles?

If two lines are cut by a transversal so that any pair of alternate exterior angles are congruent, then the lines are parallel.

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What is the Circumcenter Theorem?

The perpendicular bisectors of the sides of a triangle intersect at a point that is equidistant from the vertices of the triangle.

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What is the median of a triangle?

The median of a triangle is a line from the vertex to the midpoint of the opposite side.

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What are the parallel properties of parallelograms?

2 pairs of parallel sides of a parallelogram

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What is a regular polygon?

A polygon that is both equilateral and equiangular

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What is a quadrilateral?

A closed figure with four sides. Also know as a tetragon.

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What is a parallelogram?

A quadrilateral that has two pairs of parallel sides.

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What congruent qualities does a parallelogram have?

If a quadrilateral is a parallelogram, then its opposite sides are congruent.

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What angle qualities does a parallelogram have?

If a quadrilateral is a parallelogram, then its opposite angles are congruent.

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What qualities for consecutive kites exist?

Quadrilateral with congruent consecutive sides

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What is a trapezoid?

Quadrilateral with at least one pair of parallel sides

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What kite qualities are true?

If a quadrilateral is a kite, then its diagonals are perpendicular.

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What is a trapezoid?

A trapezoid is a quadrilateral with at least one pair of parallel sides. These sides are called bases.

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What is the sample space?

The set of all possible outcomes

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Study Notes

  • Following are facts related to geometry proofs

Proof Statements Reference Material

Sample Statements

  • Area = 25: Expected to know all formulas learned in previous grades; for example, area of a rectangle: A = lw
  • ∆ABC is a right triangle: A triangle with one right angle, Definition of Right Triangle (p GL41)
  • ∠1 = ∠3: Right angles are congruent

Segment Length and Midpoints

  • Draw AB: Through any two points, there is exactly one line, Definition of Line Segment
  • AB + BC = AC: If A, B, and C are collinear points and B is between A and C, then AB + BC = AC, Segment Addition Postulate (p 7)
  • AB = 5: The distance between two points is calculated with D = √(x2 − x1)² + (y2 − y1)², Distance Formula (p 9)
  • AC = CE: If AC = CE, then point C is the midpoint, Definition of Midpoint (p 12)
  • Point P = (4,4): The midpoint between two points is calculated with M( (x1 + x2)/2, (y1+y2)/2 ), Midpoint Formula (p 12)

Angle Measures and Angle Bisectors

  • m∠ABD = m∠DBC: If DB bisects ∠ABC, then m∠ABD = m∠DBC, Definition of Angle Bisector (p 24)
  • m∠PQS + m∠SQR = m∠PQR: If point S is in the interior of ∠PQR, then m∠PQR = m∠PQS + m∠SQR, Angle Addition Postulate (p 24)

Properties and Definitions

  • If a=b, then a+c = b+c, Addition Property of Equality (p 50)
  • If a=b, then a-c = b-c, Subtraction Property of Equality (p 50)
  • If a=b, then ac = bc, Multiplication Property of Equality (p 50)
  • If a=b and c≠0, then a/c = b/c, Division Property of Equality (p 50)
  • a = a, Reflexive Property of Equality - used when the figure is reflected (p 50)
  • If a=b, then b=a, Symmetric Property of Equality - used when the figure is rotated (p 50)
  • If a=b and b=c, then a=c, Transitive Property of Equality (p 50)
  • If a=b, then b can be substituted for a in any expression, Substitution Property of Equality (p 50)
  • JL → and JK → are opposite rays: A pair of adjacent angles whose noncommon sides are opposite rays, Definition of Linear Pair (p 52)
  • JL → and JK → form a straight line: Two rays that start from a common point and go off in exactly opposite directions, Definition of Opposite Rays (p 60)
  • m∠LJK = 180 degrees: An angle that is equal to 180 degrees, Definition of Straight Angle (p 60)
  • m∠1 = 90 degrees and m∠2 = 90 degrees: Two lines that meet at a 90-degree angle, Definition of Perpendicular Lines
  • m∠1 + m∠2 = 180 or (converse): If the sum of two angles is 180 degrees, they are supplementary, Definition of Supplementary Angles (p 52)
  • m∠1 = 90 degrees and m∠2 = 90 degrees: If ∠1 and ∠2 are congruent and supplementary, then m∠1 = 90 and m∠2 = 90, Congruent Supplementary Angles are right angles
  • m∠1 + m∠2 = 90 or (converse): If the sum of two angles is 90 degrees, they are complementary, Definition of Complementary Angles
  • m∠1 and m∠2 are supplementary or m∠1 + m∠2 = 180: If two angles form a linear pair, they are supplementary; their measures add up to 180, Linear Pair Theorem (p 52)

Proving Figures are Congruent Using Rigid Motions

  • BC = FG: Congruent means identical in shape and size; If BC = FG, then BC = FG, Definition of Congruent
  • BC ≅ FG: Two plane figures are congruent if and only if one can be obtained from the other by a sequence of rigid motions (reflections, translations, rotations); example: right angles are congruent, Definition of Congruence in Terms of Rigid Motions (p 145)

CPCFC (Corresponding Parts of Congruent Figures are Congruent)

  • BC = FG: Popular example: If two triangles are congruent then every corresponding part is congruent to each other, Corresponding Parts of Congruent Figures are Congruent (p 158) - Use CPCTC when the figure is a triangle
  • AB ≅ AB, Reflective Property of Congruence (p 160) - used when the figure is reflected
  • If AB ≅ CD then CD ≅ AB, Symmetric Property of Congruence (p 160) - used when the figure is rotated
  • If AB ≅ CD and CD ≅ EF then AB ≅ EF, Transitive Property of Congruence (p 160)

Angles Formed by Intersecting Lines

  • ∠1 ≅ ∠2: If two angles are vertical angles, then the angles are congruent, Vertical Angle Theorem (p186)
  • ∠1 ≅ ∠3: If two angles are congruent, then their supplements are congruent, Congruent Supplements Theorem (p. 194) - This looks similar to transitive
  • ∠1 ≅ ∠3: If two angles are congruent, then their complements are congruent, Congruent Complements Theorem (p. 193) - This looks similar to transitive

Transversals and Parallel Lines

  • m∠1=m∠7 or m∠2=m∠8: If two parallel lines are cut by a transversal, then the pairs of alternate exterior angles have the same measure, Alternate Exterior Angles Theorem (p 197)
  • ∠3 and ∠6 are supplementary or ∠4 and ∠5 are supplementary: If two lines are cut by a transversal, then the pairs of same-side interior angles are supplementary, Same Side Interior Angles Postulate (p 198)
  • m∠4=m∠6 or m∠3=m∠5: If two parallel lines are cut by a transversal, then the pairs of alternate interior angles have the same measure, Alternate Interior Angles Theorem (p 199)
  • m∠2=m∠6 or m∠3=m∠7 or m∠1=m∠5 or m∠4=m∠8: If two parallel lines are cut by a transversal, then the pairs of corresponding angles have the same measure, Corresponding Angles Theorem (p 200)

Parallel Lines

  • p // q (If ∠1 and ∠7 are congruent, lines are parallel): If two lines are cut by a transversal so that any pair of alternate exterior angles are congruent, then the lines are parallel, Converse of the Alternate Exterior Angles Theorem
  • p // q (If ∠3 and ∠6 are supplementary, lines are parallel): If two lines are cut by a transversal so that a pair of same-side interior angles are supplementary, then the lines are parallel, Converse of the Same-Side Interior Angles Postulate (p 210)
  • p // q : If two lines are cut by a transversal so that any pair of alternate interior angles are congruent, then the lines are parallel, Converse of the Alternate Interior Angles Theorem (p 210)
  • (If ∠4 and ∠6 are congruent, lines are parallel.): If two lines are cut by a transversal so that any pair of corresponding angles are congruent, then the lines are parallel, Converse of the Corresponding Angles Theorem (p 210)
  • m || I: Through a point P not on a line, I, there is exactly one line parallel to I, Parallel Postulate (p 212)

Perpendicular Lines

  • PA = PB: If a point is on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment, Perpendicular Bisector Theorem (p 224)
  • P is on the perpendicular bisector m of AB: If a point is equidistant from the endpoints of a segment, then it is the perpendicular bisector, Converse of the Perpendicular Bisector Theorem (p 225)

Equations of Parallel and Perpendicular Lines

  • Parallel lines have equal slopes (p 235)
  • Perpendicular lines have slopes that are negative reciprocals (p 236)
  • y = mx + b, Slope-Intercept Form
  • y-y₁ = m (x-x1), Point-Slope Form (p 235)

ASA Triangle Congruence

  • ΔABC = ADEF: If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent, ASA Triangle Congruence Theorem (p 263)

SAS Triangle Congruence

  • ΔABC = ΔDEF: If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent, SAS Triangle Congruence Theorem (p 277)

SSS Triangle Congruence

  • ∆ABC = ADEF: If three sides of one triangle are congruent to three sides of another triangle, then the triangles are congruent, SSS Triangle Congruence Theorem (p 288)

AAS Triangle Congruence

  • ΔABC = ADEF: If two angles and a non-included side of one triangle are congruent to the corresponding angles and sides and non-included sides of another triangle, then the triangles are congruent, AAS Triangle Congruence (p 320)
  • ∠1 = , ∠2: If two angles of one triangle are congruent to two angles of another triangle, then the third pair of angles are congruent, Third Angles Theorem (p 321)

HL Triangle Congruence

  • ∆ABC = ADEF: If the hypotenuse and a leg of a right triangle are congruent to the hypotenuse and a leg of another right triangle, then the triangles are congruent, Hypotenuse-Leg (HL) Congruence Theorem (p 332)

Interior and Exterior Angles

  • m∠A+m∠B+m∠C= The sum of the angle measures of a triangle is 180, Triangle Sum Theorem (p 351)
  • Sum Interior ∠ = (n-2)180: The sum of the measures of the interior angles of a convex polygon with n sides is (n-2)(180), Polygon Angles Sum Theorem (p 353)
  • m∠4=m∠1+m∠2: The measure of an exterior angle of a triangle is equal to the sum of the measures of the remote interior angles, Exterior Angle Theorem (p 356)

Isosceles and Equilateral Triangles

  • An isosceles triangle is a triangle with at least 2 congruent sides, Definition of Isosceles Triangle (p 367)
  • ∠B = ∠C (If AB = AC then ∠B = ∠C), If two sides of a triangle are congruent, then the two angles opposite the sides are congruent; base angles of an isosceles triangle are congruent, Isosceles Triangle Theorem (p 368) also called Base Angles Theorem
  • AB = AC (If ∠B = ∠C,then AB = AC), If two angles of a triangle are congruent, then the two sides opposite the angles are congruent, Converse of the Isosceles Triangle Theorem
  • ∠A = ∠B = ∠C: If a triangle is equilateral, then it is equiangular, Equilateral Triangle Theorem (p 370)
  • If a triangle is equiangular, then it is equilateral, Converse of the Equilateral Triangle Theorem (p 370)

Triangle Inequalities

  • AB + BC > AC or BC + AC > AB or AC + AB > BC, The sum of any two side lengths of a triangle is greater than the third side length, Triangle Inequality Theorem (p 383)
  • m∠B>m∠A (If AC > BC then m∠B > m∠A), If two sides of a triangle are not congruent, then the larger angle is opposite the longer side, Side-Angle Relationship in Triangles Op (p 387)
  • AC > BC (If m∠B > m∠A then AC > BC), If two angles of a triangle are not congruent, then the longer side is opposite the larger angle, Angle-Side Relationship in Triangles (p 388)

Perpendicular Bisectors of Triangles

  • Drawing perpendicular bisectors -> point of concurrency is the circumcenter -> inside, outside, or on triangle
  • AP ≅ BP ≅ CP: The perpendicular bisectors of the sides of a triangle intersect at a point that is equidistant from the vertices of the triangle, Circumcenter Theorem (p 402)

Angle Bisectors of Triangles

  • Drawing angle bisectors -> point of concurrency is the incenter -> always inside the triangle
  • AC = BC (If ∠APC = ∠BPC then AC = BC): If a point is on the bisector of an angle, then it is equidistant from the sides of an angle, Angle Bisector Theorem (p 414)
  • ∠APC = ∠BPC: If a point in the interior of an angle is equidistant from the sides of the angle, then it is on the bisector of the angle, Converse of the Angle Bisector Theorem (p 414)
  • PX = PY = PZ: The angle bisectors of a triangle intersect at a point that is equidistant from the sides of the triangle, Incenter Theorem (p 416)
  • AP = BP = CP: The point where the perpendicular bisectors of each side of a triangle intersect; this point is Equidistant from vertices, Definition of Circumcenter (p 417) - This is a theorem also
  • PX = PY = PZ: The point where the angle bisectors of each angle of a triangle meet; points are Equidistant from sides and Always inside a triangle, Definition of Incenter (p 417) - This is a Theorem also

Medians and Altitudes of Triangles

  • Drawing medians -> the point of concurrency is the centroid -> always inside the triangle
  • Drawing altitudes -> the point of concurrency is the orthocenter -> can be inside, outside, or on triangle
  • AP = CP: The median of a triangle is a line from the vertex to the midpoint of the opposite side, Definition of Median of a Triangle (p 423)
  • AP = ⅔ AX: The centroid of a triangle is located ⅔ of the distance from each vertex to the midpoint of the opposite side, Centroid Theorem (p 425) - Also called the Concurrency of Medians Theorem (p 578)
  • The perpendicular segment from vertex to the line containing the other side of the triangle, Definition of Altitude (p 429)
  • The orthocenter of a triangle is the point where the altitudes of each triangle meet, Definition of Orthocenter of a Triangle (p 429)

Midsegments of Triangles

  • Point P is the midpoint of AB: The line segment that connects the midpoints of two sides of the triangle, Definition of Midsegment (p 439)
  • UW = ½ ST and UW is parallel to ST: The segment joining the midpoints of two sides of a triangle is parallel to the third side, and its length is half the length of that side, Triangle Midsegment Theorem (p 443)

Properties of Parallelogram

  • Parallelogram definition: 2 pairs of // sides
  • Opposite sides are congruent in a Parallelogram
  • Opposite angles are congruent in a Parallelogram
  • Diagonals bisect each other in a Parallelogram
  • ∠A = ∠B = ∠C and/or AB = BC = CA: A polygon that is both equilateral and equiangular, Definition of Regular Polygon (glossary)
  • AB || CD and AD || BC: Quadrilateral that has two pairs of parallel sides, Definition of parallelogram (p 465)
  • ∠1 and ∠2 are supplementary: Because of the parallel lines of the parallelogram, this is the same as Same Side Interior Angles Postulate, Consecutive angles of a parallelogram are supplementary
  • AB ≅ CD and AD ≅ BC: If a quadrilateral is a parallelogram, then its opposite sides are congruent (p 467)
  • ∠ADC ≅ ∠CBA and ∠DAB ≅ ∠BCA: If a quadrilateral is a parallelogram, then its opposite angles are congruent (p 468)
  • EA ≅ EC and ED ≅ EB: If a quadrilateral is a parallelogram, then its diagonals bisect each other (p 469)

Conditions of Parallelogram

  • Look for two pairs of opposite congruent sides to identify a parallelogram: If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram (p 481)
  • Look for one pair of congruent and parallel sides to identify a parallelogram: If one pair of opposite sides are congruent and parallel, then the quadrilateral is a parallelogram (p 482)
  • Look for two pairs of opposite congruent angles to identify a parallelogram: If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram (p 482)
  • Look for bisecting diagonals to identify a parallelogram: If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram (p 483)

Properties of Rectangles, Rhombuses, and Squares

  • Parallelogram properties include: 2 pairs of // sides, opposite sides are congruent, opposite angles are congruent, and diagonals bisect each other
  • Rectangle Definition: Quadrilateral with 4 right angles
  • Rectangle Diagonals: Congruent
  • Rhombus Definition: Quadrilateral with 4 congruent sides
  • Rhombus Angles: Diagonals bisect angles
  • Rhombus Diagonals: ⊥
  • Square Definition: Quadrilateral with 4 right angles and 4 congruent sides
  • Square Angles: Diagonals bisect angles
  • Square Diagonals: Congruent and ⊥
  • m∠A = m∠B = m∠C = m∠D = 90 degrees: A rectangle is a quadrilateral with four right angles, Definition of Rectangle (p 495)

Conditions for Rectangles, Rhombuses, and Squares

  • Look for congruent diagonals to identify a rectangle: If a parallelogram is a rectangle, then its diagonals are congruent (p 496)
  • Defintion of a Rhombus: A rhombus is a quadrilateral with four congruent sides (p 497)
  • Look for diagonals that are perpendicular to identify a rhombus: If a parallelogram is a rhombus, then its diagonals are perpendicular (p 497)
  • Look for diagonals bisecting pairs of opposite angles to identify a rhombus. If a parallelogram is a rhombus, then each diagonal bisects a pair of opposite angles (p 497 cont.)
  • Look for one angle to identify a rectangle: If one angle of a parallelogram is a right angle, then the parallelogram is a rectangle (p 509)
  • Look for congruent diagonals to identify a rectangle: If the diagonals of a parallelogram are congruent, then the parallelogram is a rectangle (p 509)
  • Look for one pair of consecutive congruent sides to identify a rhombus: If one pair of consecutive sides of a parallelogram are congruent, then the parallelogram is a rhombus (p 510)
  • Look for perpendicular diagonals to identify a rhombus: If the diagonals of a parallelogram are perpendicular, then the parallelogram is a rhombus (p 510)
  • Look for one diagonal to bisect a pair of opposite angles to identify a rhombus: If one diagonal of a parallelogram bisects a pair of opposite angles, then the parallelogram is a rhombus (p 510)
  • A quadrilateral with four congruent sides and four right angles, Definition of Square (p 512)

Conditions for Kites and Trapezoids

  • Kite definition: Quadrilateral with congruent consecutive sides
  • Kite angles: One pair of opposite congruent angles
  • Kite diagonals: ⊥ one Another, one bisects the other diagonal and the pair of opposite non congruent angles
  • Trapezoid definition: Quadrilateral with at least one pair of parallel sides
  • Trapezoid Isosceles: Congruent legs that are not parallel
  • Trapezoid Isosceles Angles: Base angles are congruent
  • Trapezoid Isosceles Diagonals: Congruent
  • A kite is a quadrilateral with congruent consecutive sides, Definition of a Kite (p 519)
  • Look for perpendicular diagonals to identify a kite: If a quadrilateral is a kite, then its diagonals are perpendicular
  • Look for exactly one pair of opposite congruent angles to identify a kite: If a quadrilateral is a kite, then exactly one pair of opposite angles are congruent
  • Look for one diagonal to bisect the pair of non-congruent angles to identify a kite: If a quadrilateral is a kite, then one of the diagonals bisects the pair of non-congruent angles
  • Look for exactly one diagonal to bisect the other to identify a kite: If a quadrilateral is a kite, then exactly one diagonal bisects the other (p 520)
  • A trapezoid is a quadrilateral with at least one pair of parallel sides and these sides are called bases, Definition of a Trapezoid (p 521)
  • A trapezoid with congruent legs that are not parallel, Definition of Isosceles Trapezoid (p 521)
  • Look for both pairs of base angles on a quadrilateral to be congruent to identify an isosceles trapezoid: If a quadrilateral is an isosceles trapezoid, then each pair of base angles are congruent (p 522)
  • Look for one pair of congruent base angles on a trapezoid to identify an isosceles trapezoid: If a trapezoid has one pair of congruent base angles, then the trapezoid is isosceles
  • Look for congruent diagonals on a trapezoid to identify an isosceles trapezoid: A trapezoid is isosceles if and only if its diagonals are congruent (p 522)
  • XY is parallel to BC and XY is parallel to AD then XY = (BC + AD): The mid-segment of a trapezoid is parallel to each base, and its length is one-half the sum of both the bases, Trapezoid Midsegment Theorem (p 525)

Slope and Parallel Lines

  • Slope = (y2-y1)/(x2-x1), Slope Formula (p 543)
  • Two nonvertical lines are parallel if and only if they have the same slope, Slope Criteria for Parallel Lines Theorem (p 543)

Slope and Perpendicular Lines

  • Two nonvertical lines are perpendicular if and only if the product of their slope is -1, Slope Criteria for Perpendicular Lines Theorem (p 559)

Perimeter and Area on Coordinate Plane

  • A=½bh, Area of a Triangle (p 602)
  • A=bh, Area of a Rectangle (p 602)
  • A=bh, Area of Parallelogram (p 602)
  • A=½d₁d₂, Area of Rhombus (p 602)
  • A=½d₁d₂, Area of Kite (p 602)
  • A=½(b₁+b₂)h, Area of Trapezoid (p 602)
  • The area of a region is equal to the sum of the areas of its non overlapping parts, Area Addition Postulate (p 604)

Dilations

  • A transformation that can change the size of a polygon but leaves the shape unchanged, Definition of Dilation (p 629)
  • Ratio of: (image corresponding side)/(preimage corresponding side) = Dilation Scale Factor (p 631)
  • The fixed point about which all other points are transformed by a dilation is called, Definition of Center of Dilation (p 631)

Proving Figures are Similar Using Transformations

  • All circles are similar, Circle Similarity Theorem (p 646)

Corresponding Part of Similar Figures

  • If ∆ABC~∆XYZ then ∠A=∠X, ∠B=∠Y, ∠C=∠Z
  • Corresponding angles of similar figures are congruent.
  • If ∆ABC~∆XYZ then AB/XY = BC/YZ = AC/XZ
  • Corresponding sides of similar figures are proportional (p 657)

AA Similarity of Triangles

  • If two angles of one triangle are congruent to two angles of another triangle, then the two triangles are similar, Angle-Angle (AA) Similarity Theorem (p 666)

If three sides of one triangle are proportional to the corresponding sides of another triangle, then the triangles are similar

Side-Side-Side (SSS) Triangle Similarity Theorem (p 669)

Triangle Proportionality Theorem

  • If a line is parallel to a side of a triangle intersects the other two sides, then it divides those sides proportionally (p 688)
  • If a line is parallel to a side of a triangle intersects the other two sides, then it divides those sides proportionally, Converse of the Triangle Proportionality Theorem (p 691)

Similarity in Right Triangles

  • The altitude to the hypotenuse of a right triangle forms 2 triangles that are similar to the original triangle and to each other p 728 (Right Triangle Hypotenuse Theorem or Geometric Theorem)
  • If the altitude intersects the hypotenuse at x and y, and h is the altitude then the the Geometric Mean Theorem reads as h=√xy where h is the altitude and x and y are the two line segments of the hypotenuse as split by the altitude (p 728)
  • If the altitude intersects the hypotenuse at y and c, and b is the leg then the Geometric Theorem reads as b=√yc where b is a leg of the right triangle, c is the total length of the hypotenuse, and y is the segment closest to b as split by the altitude (p 728)

Pythagorean Theorem

  • a² + b² = c²: In a right triangle, the square of the sum of the lengths of the legs is equal to the square of the length of the hypotenuse (p 730)

Tangent Ratio

  • tan m∠A = (length of leg opposite ∠A)/(length of leg adjacent ∠A), Tangent of an Angle (p 750) If tan m∠A = (length of leg opposite ∠A)/(length of leg adjacent ∠A,) then m∠A = tan⁻¹ (length of leg opposite ∠A)/(length of leg adjacent ∠A), Inverse Tangent of an Angle (p 752)

Sine and Cosine Ratios

  • sin m∠A = (length of leg opposite ∠A)/(length of hypotenuse), Sine of an Angle (p 760)
  • cos m∠A = (length of leg adjacent ∠A)/(length of hypotenuse), Cosine of an Angle (p 760)
  • Given θ (or A) is an acute angle of a right triangle, 90-θ (or B) is the other acute angle, sin (θ) = cos (90-θ) or cos (θ) = sin (90-θ), Trigonometric Ratios of Complementary Angles (p 761)
  • Given the sides of a right triangle and sin m∠A = (length of leg opposite ∠A)/(length of hypotenuse), it can be stated m∠A = sin⁻¹ (length of leg opposite ∠A) / (length of hypotenuse) , Inverse Sine of an Angle (p 763)
  • Given the sides of a right triangle and cos m∠A = (length of leg adjacent ∠A)/(length of hypotenuse); It can be written m∠A= cos⁻¹ m∠A = (length of leg adjacent ∠A)/(length of hypotenuse), Inverse cosine of an Angle (p 763)

Special Right Triangles

  • 45-45-90 (ratio is 1 : 1 : √2): sin(45°) = √2/2 cos(45°) = √2/2 tan(45°) = 1
  • 30-60-90 (ratio is 1: √3 : 2): sin(30°) = 1/2 cos(30°) = √3/2 tan(30°) = √3/3 sin(60°) = √3/2 cos(60°) = 1/2 tan(60°) = √3

Examples of Pythagorean Triples

  • Examples include 3-4-5, 5-12-13, 7-24-25, 8-15-17
  • Set of positive integers a,b, and c that satisfy a² + b² = c²; Triangles that have non-integers sides do not form Pythagorean Triples.

Problem Solving with Trigonometry

  • Area = ½bc sinA = ½ac sinB = ½ab sinC: Area Formula in Terms of It's Side Lengths (uses two side lengths and the included angle)

Central and Inscribed Angles

  • Segment whose endpoints lie on a circle, Definition of Chord (p 813)
  • Angle less than 180 degrees whose vertex lies at the center of the circle, Definition of Central Angle (p 813)
  • Angle whose vertex lies on the circle and whose sides contain chords of the circle , Definition of Inscribed Angle (p 813)
  • A minor arc is an arc whose points are on or in the interior of a corresponding central angle, Definition of Minor Arc (p 815)
  • A major arc is an arc whose points are on or in the exterior of a corresponding central angle, Definition of Major Arc (p 815)
  • A semicircle is an arc whose endpoints are the endpoints of a diameter, Definition of Semicircle (p 815)
  • ADB = mAD + mDB; The measure of an arc formed by two adjacent arcs is the sum of the measures of the two arcs, Arc Addition Postulate (p 815)
  • m∠ADB = ½ mAB; The measure of an inscribed angle is half the measure of its intercepted arc, Inscribed Angle Theorem (p 817)
  • The endpoints of a diameter lie on an inscribed angle if and only if the inscribed angle is a right angle, Inscribed Angle of a Diameter Theorem (p 820)

Angles Inscribed in Quadrilaterals

  • If a quadrilateral is inscribed in a circle, then its opposite angles are supplementary, Inscribed Quadrilateral Theorem (p 830)

Tangents and Circumscribed Angles

  • A line in the same plane as a circle that intersects the circle in exactly one point, the point of tangency, Definition of Tangent (p 841)
  • If a line is tangent to a circle, then it is perpendicular to a radius drawn to the point of tangency, Tangent-Radius Theorem (p 842)
  • If a line is perpendicular to a radius of a circle at a point on the circle, then it is tangent to the circle at that point on the circle, Converse of the Tangent-Radius Theorem (p 843)
  • An angle formed by two rays from a common endpoint that are both tangent to the circle, Definition of Circumscribed Angle (p 845)
  • A circumscribed angle of a circle and its associated central angle are supplementary, Circumscribed Angle Theorem (p 845)

Segment Relationships in Circles

  • (AE)(EB)=(CE)(ED): If two chords intersect inside a circle, then the products of the lengths of the segments of the chords are equal, Chord-Chord Product Theorem (p 854)
  • Definition of Secant (p 856): any line that intersects a circle in exactly two points
  • (AE)(BE) = (CE)(DE): If two secants intersect in the exterior of a circle, then the product of the lengths of one secant segment and its external segment equals the product of the lengths of the other secant segment and its external segment Secant-Secant Product Theorem (p 856)
  • (AC)(BC) = (DC)²: If a secant and a tangent intersect in the exterior of a circle, then the product of the lengths of the secant segment and its external segment equals the length of the tangent segment squared, Secant-Tangent Product Theorem (p 858)
  • If a tangent and a secant intersect in the exterior of a circle, then the measure of the angle formed is half the distance of the measures of its intercepted arcs, Tangent-Secant Exterior Angle Measure Theorem (p 874 - 1st of 3)
  • If two tangents intersect in the exterior of a circle, then the measure of the angle formed is half the distance of the measures of its intercepted arcs, Tangent-Secant Exterior Angle Measure Theorem (p 874 - 2nd of 3)
  • If two secants intersect in the exterior of a circle, then the measure of the angle formed is half the distance of the measures of its intercepted arcs, Tangent-Secant Exterior Angle Measure Theorem (p 874 - 3rd of 3)
  • C = 2πΓ r = radius Circle Circumference Formula (p 895)
  • Α = πr² r = radius Circle Area Formula (p 897)

Arc and Radian Measure

  • s = (m/360)(2πr) s = arc length (in length units) m = degree measure of arc r = radius r Arc Length Formula (p 906)
  • m°=(m/360)(2)π radians Radians is a unit of angle measurement conversion: (m/360)(2)π where m is the degree, Radian Measure (p 908)

Benchmark Angles (p 911)

| Degree Measure | 0° | 30° | 45° | 60° | 90° | 120° | 135° | 150° | 180° | | Radan Measure | 0 | π/6 | π/4 | π/3 | π/2 | 2π/3 | 3π/4 | 5π/6 | π |

Sector Area

  • A = (m/360) πr²: where m = degree measure of arc and r = radius is; Area of a Sector (p 916)

Equation of Circle

  • (x-h)² + (y-k)² = r²: where Center of circle=(h,k) and radius=r is; Equation of a Circle (p 926)

Volume of Prisms and Cylinders

  • Prism where lateral edges that are perpendicular to the bases and all faces are rectangles, Definition of Right Prism (p 949)
  • Bases are perpendicular to the center axis, Definition of Right Cylinder (p 949)
  • V = bh: b area of base, h = height, General formula for Volume of Prism (p 950)
  • V = Iwh; where I = length is; Volume of a Right Rectangular Prism (p 950)
  • V = s³ where s = side length, Volume of a Cube (p 950)
  • Prism having at least one non-rectangular lateral face, Definition of Oblique Prism (p 952)
  • Cylinder whose axis is not perpendicular to the bases, Definition of Oblique Cylinder (p 952)
  • Cavalieri's Principle (p 953): If the altitude (h) lies outside the base of the prism and if two solids have the same height and the same cross sectional area at every level, then the two solids have the same volume
  • Vtotal = V1 + V2: Total volume equals the sum of the volumes of each shape composing the total figure, Volume of Composite Figures (p 954)

Volume of Pyramids

  • The top or highest point of something, Definition of Apex
  • Pyramids that have equal base areas and equal heights have equal volumes, Pyramid Volume Postulate (p 963)
  • V = ⅓bh, where b is a base and h is the height, Volume of a Pyramid (p 965)
  • V = ⅓πr²h or V = ⅓Bh Volume of Cone (p 979)

Volume of Spheres

  • A region of a plane that intersects a solid figure, Definition of Cross Section (p 991)
  • V =

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