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Questions and Answers

In triangle LMN, where angle L = 30°, angle N = 60°, and angle M = 90°, how does the length of side MN relate to the length of side LN?

  • MN is $\sqrt{3}$ times the length of LN.
  • MN is half the length of LN. (correct)
  • MN is equal to LN.
  • MN is twice the length of LN.

In triangle LMN, with angles L = 30°, N = 60°, and M = 90°, if LN = 10 cm, what is the length of LM?

  • 15 cm
  • 5 cm
  • 10 cm
  • $5\sqrt{3}$ cm (correct)

A right-angled triangle has acute angles of 45° and 45°. If the hypotenuse is $7\sqrt{2}$ cm, what is the length of each of the perpendicular sides?

  • $7\sqrt{2}$ cm
  • 14 cm
  • 3.5 cm
  • 7 cm (correct)

In triangle PQR, angle P = 45°, angle Q = 45°, and angle R = 90°. Which statement accurately describes the relationship between the sides?

<p>PR = QR (A)</p> Signup and view all the answers

Triangle XYZ has angles X = 30°, Y = 60°, and Z = 90°. If XY (the hypotenuse) is 12 cm, what is the area of triangle XYZ?

<p>$18\sqrt{3}$ cm$^2$ (A)</p> Signup and view all the answers

In triangle ABC, point D lies on side AC. If AD = 7 and DC = 9, how does the ratio of the area of triangle ABD to the area of triangle BDC relate?

<p>The ratio A(ABD) / A(BDC) is equal to 7/9 because the triangles share the same height from vertex B. (D)</p> Signup and view all the answers

Given two triangles with equal areas but different base lengths, how are their corresponding heights related?

<p>The heights are inversely proportional to the base lengths. (C)</p> Signup and view all the answers

Given that $\angle APB = \angle AQC$, which additional piece of information is LEAST helpful in proving that $\triangle APB \sim \triangle AQC$ using the Angle-Angle (AA) similarity test?

<p>$AB \parallel AC$ (C)</p> Signup and view all the answers

Triangle PQR has base PR and height QT, while triangle XYZ has base XZ and height YW. If PR = 2 * XZ and the area of triangle PQR is equal to the area of triangle XYZ, what is the ratio of YW to QT?

<p>2:1 (A)</p> Signup and view all the answers

In quadrilateral $ABCD$, diagonals intersect at point $Q$. Given $2QA = QC$ and $2QB = QD$, which of the following statements CANNOT be directly concluded?

<p>$AQ = QB$ (C)</p> Signup and view all the answers

In triangles ABC and BCD, AD || BC, with AP perpendicular to BC. What conclusion can be drawn about the areas of these triangles?

<p>A(ABC)= A(BCD) since they lie between the same parallels and have equal bases. (C)</p> Signup and view all the answers

If $\triangle ABC$ and $\triangle EDC$ share $\angle C$, and $\angle ABC = 75^\circ$ and $\angle EDC = 75^\circ$, what additional information would be SUFFICIENT to prove $\triangle ABC \sim \triangle EDC$ using only the Angle-Angle (AA) similarity criterion?

<p>$\angle BAC = \angle DEC$ (B)</p> Signup and view all the answers

Given two triangles, one with base $b_1$ and height $h_1$, and the other with base $b_2$ and height $h_2$, such that $b_1 = 2b_2$ and $h_2 = 4h_1$, what is the ratio of the area of the first triangle to the area of the second triangle?

<p>1:2 (C)</p> Signup and view all the answers

Given $\triangle ABC$ and $\triangle MNP$ are two triangles. Which condition MUST be met to certainly prove that the two triangles are NOT similar?

<p>The ratio of two sides of one triangle is not equal to the ratio of two sides of the other triangle. (B)</p> Signup and view all the answers

In quadrilateral $ABCD$, diagonals intersect at $Q$. If $2QA = QC$ and $2QB = QD$, and it is proven that $CD = 2AB$, which similarity test is MOST directly used to initially establish $\triangle AQB \sim \triangle CQD$?

<p>SAS (Side-Angle-Side) (C)</p> Signup and view all the answers

If the ratio of the areas of two similar triangles is 9:16, what is the ratio of their corresponding heights?

<p>3:4 (D)</p> Signup and view all the answers

In $\triangle ABC$ and $\triangle EDC$, given $\angle ABC = 75^\circ$ and $\angle EDC = 75^\circ$, what is a sufficient condition to prove their similarity through Angle-Angle (AA) test, assuming one-to-one correspondence of vertices as $A \leftrightarrow E$, $B \leftrightarrow D$, and $C \leftrightarrow C$?

<p>$\angle BAC \cong \angle DEC$ (C)</p> Signup and view all the answers

Consider triangle ABC, where PQ is perpendicular to BC and AD is perpendicular to BC. If the length of PQ is half the length of AD, how does the area of triangle PBC relate to the area of triangle ABC, assuming the base BC is common to both triangles?

<p>A(PBC) = 0.5 * A(ABC) (B)</p> Signup and view all the answers

Consider $\triangle APB$ and $\triangle AQC$ where $BP \perp AC$ and $CQ \perp AB$. What additional congruence MUST be shown to prove $\triangle APB \cong \triangle AQC$ by Angle-Angle-Side (AAS) congruence?

<p>All mentioned options. (D)</p> Signup and view all the answers

Two triangles share a common base. The altitude of the first triangle is 7 cm and its area is 84 sq cm. If the area of the second triangle is 54 sq cm, what is the length of its altitude?

<p>4.5 cm (B)</p> Signup and view all the answers

If diagonals of quadrilateral $ABCD$ intersect at $Q$ such that $2QA = QC$ and $2QB = QD$, which statement accurately describes the relationship between the areas of $\triangle AQB$ and $\triangle CQD$?

<p>Area($\triangle CQD$) = 4 * Area($\triangle AQB$) (A)</p> Signup and view all the answers

In a right-angled triangle XYZ where angle XZY is 90 degrees and angle XYZ is 45 degrees, hypotenuse ZY is known. Which of the following statements accurately describes the relationship between the sides?

<p>XY and XZ are each (\frac{1}{\sqrt{2}}) times the length of ZY. (C)</p> Signup and view all the answers

If ZY = $3\sqrt{2}$ cm in a 45-45-90 triangle XYZ, what are the lengths of sides XY and XZ?

<p>XY = 3 cm, XZ = 3 cm (C)</p> Signup and view all the answers

Consider an isosceles right-angled triangle formed using the hypotenuse of two congruent right-angled triangles. How does combining these figures (two congruent right triangles, and one isosceles right triangle) allow for an alternative proof of the Pythagorean theorem?

<p>By constructing a trapezium and equating its area (calculated two different ways) which relates the sides of right triangles, echoing the Pythagorean relationship. (B)</p> Signup and view all the answers

In the context of proving the Pythagorean theorem using similar triangles, what role do properties of similar triangles play?

<p>They establish a direct proportionality between corresponding sides, leading to equations that demonstrate the theorem's validity. (C)</p> Signup and view all the answers

When constructing a proof of the Pythagorean theorem using a trapezium formed by right-angled triangles, which of the following statements regarding the relationships between the triangle's sides and the trapezium's characteristics is true?

<p>The parallel sides of the trapezium correspond to the two shorter sides (legs) of the right-angled triangles, and the area of the trapezium can be expressed in terms of these sides and the hypotenuse. (C)</p> Signup and view all the answers

Suppose you are tasked with visually demonstrating the Pythagorean theorem to a group of students using geometric shapes. What would be the MOST effective approach to illustrate the relationship $a^2 + b^2 = c^2$?

<p>Construct squares on each side of a right triangle and visually demonstrate that the sum of the areas of the squares on the two shorter sides equals the area of the square on the longest side (hypotenuse). (A)</p> Signup and view all the answers

Imagine you are teaching the Pythagorean theorem using similar triangles. You start by drawing a right triangle and then draw an altitude from the right angle to the hypotenuse. Which of the following statements correctly uses the properties of similar triangles created in this construction to prove the theorem?

<p>The newly formed triangles are similar to the original triangle and to each other, thus ratios of corresponding sides can be set equal, ultimately deriving $a^2 + b^2 = c^2$. (A)</p> Signup and view all the answers

A student attempts to prove the Pythagorean theorem using a diagram involving areas of triangles but makes an error by assuming one of the triangles is equilateral instead of remaining as a right triangle. What is the MOST likely outcome of this error on the proof?

<p>The error invalidates the proof because the fundamental relationships between sides of the right triangles have been altered, leading to an incorrect conclusion. (A)</p> Signup and view all the answers

In $\triangle ABC$, given $AD \perp BC$, and applying the Pythagorean theorem, which of the following derivations correctly relates the sides?

<p>$AB^2 + CD^2 = AC^2 + BD^2$, derived by equating expressions for $AD^2$ in $\triangle ADC$ and $\triangle ADB$. (A)</p> Signup and view all the answers

Given $\triangle LMN$ with sides $l=5$, $m=13$, and $n=12$, what justifies the conclusion that $\triangle LMN$ is a right-angled triangle?

<p>The square of the longest side, $m^2$, is equal to the sum of the squares of the other two sides, $l^2 + n^2$. (B)</p> Signup and view all the answers

In $\triangle PQR$, right-angled at $Q$, if $PQ = 9$ cm and $QR = 12$ cm, how does varying the lengths of $PQ$ and $QR$ proportionally affect the length of the hypotenuse $PR$?

<p>If $PQ$ and $QR$ are both multiplied by a factor of $k$, $PR$ is multiplied by $k$. (D)</p> Signup and view all the answers

What is the most accurate interpretation of a Pythagorean triplet? (Select all that apply)

<p>A set of three positive integers $a$, $b$, and $c$, such that $a^2 + b^2 = c^2$. (B)</p> Signup and view all the answers

Given $\triangle MNP$ with $\angle MNP = 90$ and $NQ \perp MP$, $MQ = 9$, $QP = 4$. If the length of $MQ$ is increased by $x$ and $QP$ is decreased by $x$, what value of $x$ would result in $NQ$ doubling, assuming $NQ$ was initially calculated?

<p>The value of $x$ depends on the initial calculation of $NQ$ and requires solving a quadratic equation. (C)</p> Signup and view all the answers

In $\triangle QPR$ with $\angle QPR = 90$, $PM \perp QR$, $Q-M-R$, $PM = 10$, $QM = 8$. How does changing the length of PM affect the relationship between QM and MR?

<p>Altering PM will change MR such that the product $PM^2 = QM \cdot MR$ remains constant, as per geometric mean theorem . (C)</p> Signup and view all the answers

In $\triangle ABC$, $AD$ is an altitude to side $BC$. If $AB^2 + CD^2 = BD^2 + AC^2$, which statement about the relationship represents a valid deduction based solely on the Pythagorean theorem?

<p>The equality is derived from applying Pythagoras theorem to $\triangle ADC$ and $\triangle ADB$ and manipulating the resulting equations. (A)</p> Signup and view all the answers

Given that (3, 5, 4) are sides of a triangle, assess whether they form a Pythagorean triplet and explain the mathematical reasoning.

<p>Yes, because $3^2 + 4^2 = 5^2$ satisfies the Pythagorean theorem. (B)</p> Signup and view all the answers

Flashcards

Area Ratio (Equal Heights)

Triangles with equal heights have areas proportional to their bases.

Area Ratio (Equal Bases)

Triangles with equal bases have areas proportional to their heights.

Area Ratio (General)

The ratio of areas of two triangles is equal to the ratio of the products of their bases and corresponding heights.

Perpendicular Heights

If BC is perpendicular to AB, and AD is perpendicular to AB, the triangles ABC and ADB share a common base AB.

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Ratio involving parallel lines

The area of triangle ABC divided by area of triangle BCD, given AP is perpendicular to BC, and AD is parallel to BC.

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Variable Triangle Height

seg PS is perpendicular to seg RQ and seg QT is perpendicular to seg PR

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Perpendicular Sides

If PQ is perpendicular to BC, and AD is perpendicular to BC. Consider what sides are perpendicular.

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Parallel Line height

When two lines are parallel, this means that they have the same height

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AA Test of Similarity

Triangles are similar if two angles of one triangle are congruent to two angles of the other triangle.

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SAS Test of Similarity

If two sides are proportional and the included angles are congruent, then the triangles are similar.

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Opposite Angles

Angles located directly opposite each other when two lines intersect.

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Similar Triangles & Proportional Sides

Corresponding sides of similar triangles are in proportion to each other.

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Perpendicular

A line segment perpendicular to another line segment forming a right angle.

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Similar Triangles

Triangles having same shape, but different sizes.

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Proportion

A statement of equality between two ratios.

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Corresponding Sides of Similar Triangles

The ratio of corresponding sides in similar triangles are equal.

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30°-60°-90° Triangle (Side opposite 30°)

In a 30°-60°-90° triangle, the side opposite the 30° angle is half the length of the hypotenuse.

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30°-60°-90° Triangle (Side opposite 60°)

In a 30°-60°-90° triangle, the side opposite the 60° angle is (√3 / 2) times the length of the hypotenuse.

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30°-60°-90° Example

In a 30°-60°-90° triangle with hypotenuse LN = 6 cm, the side opposite 30° (MN) is 3 cm and the side opposite 60° (LM) is 3√3 cm.

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45°-45°-90° Triangle Property

In a 45°-45°-90° triangle, each leg (perpendicular side) is (1/√2) times the length of the hypotenuse.

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45-45-90 Triangle Definition

A triangle with angles measuring 45°, 45°, and 90°.

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45-45-90 Triangle Side Ratios

In a 45-45-90 triangle, if ZY is the length of one leg, then XY = XZ = (1/√2) * ZY.

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45-45-90 Triangle Example

If ZY = 3√2 cm in a 45-45-90 triangle, then XY = XZ = 3 cm.

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Pythagorean Theorem Proof

Proving the theorem of Pythagoras using areas of right angled triangles and a square.

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Area of a Trapezium

Area = 1/2 * (sum of parallel sides) * height

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Area Summation

Area of trapezium = Sum of areas of the three right-angled triangles.

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Pythagoras: Similar Triangles

Theorem based on properties of similar triangles.

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Geometric Mean Theorem

In a right triangle, the altitude to the hypotenuse divides the triangle into two triangles that are similar to the original triangle and to each other.

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Geometric Mean Formula

QS² = PS * SR; seg QS is the geometric mean of seg PS and seg SR.

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Pythagorean Theorem

In a right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides: a² + b² = c²

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Converse of Pythagorean Theorem

If a² + b² = c² in a triangle, then the triangle is a right triangle.

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Right Triangle Side Ratio (30°)

If one side is half the hypotenuse, the angle opposite that side is 30°.

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30°-60°-90° Theorem (side opposite 30°)

In a 30°-60°-90° triangle, the side opposite the 30° angle is half the hypotenuse.

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30°-60°-90° Theorem (side opposite 60°)

In a 30°-60°-90° triangle, the side opposite the 60° angle is √3/2 times the hypotenuse.

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45°-45°-90° Theorem

In a 45°-45°-90° triangle, the legs are congruent, and each leg is 1/√2 times the hypotenuse

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Study Notes

Mathematics Part - II Standard X

Fundamental Duties (Article 51A)

  • It is the duty of every citizen of India to abide by the Constitution and respect its ideals and institutions, the National Flag and the National Anthem.
  • Citizens should cherish and follow the noble ideals that inspired the national struggle for freedom.
  • Citizens must uphold and protect the sovereignty, unity, and integrity of India.
  • Citizens should defend the country and render national service when called upon to do so.
  • Citizens must promote harmony and the spirit of common brotherhood amongst all the people of India transcending religious, linguistic, and regional or sectional diversities, and renounce practices derogatory to the dignity of women.
  • Citizens should value and preserve the rich heritage of composite culture.
  • Citizens must protect and improve the natural environment, including forests, lakes, rivers, and wildlife, and have compassion for living creatures.
  • Citizens should develop scientific temper, humanism, and the spirit of inquiry and reform.
  • Citizens should safeguard public property and abjure violence.
  • Citizens must strive towards excellence in all spheres of individual and collective activity so that the nation constantly rises to higher levels of endeavor and achievement.
  • A parent or guardian must provide opportunities for education to their child or ward between the ages of six and fourteen years.

Preface

  • Mathematics Part-II includes Geometry, Trigonometry, Coordinate geometry and Mensuration
  • This book aims to provide a lucid explanation of new units, formulas, or applications.
  • Each chapter provides examples with practice questions
  • Star-marked questions indicate challenging problems for talented students
  • The "For more Information" section assists students who want to continue studying mathematics after tenth standard.
  • Additional audio-visual material is available via QR codes
  • Focus is on preparing thoroughly for the tenth standard examination.

Competencies to be developed

  • After studying this book students will be able to:
  • Solve examples using properties of similar triangles, congruent triangles, and the Pythagoras theorem.
  • Construct similar triangles.
  • Use properties of chords and tangents.
  • Construct tangents to a circle.
  • Find the distance between two points.
  • Find the co-ordinates of a point dividing a segment in a given ratio.
  • Find the slope of a line.
  • Find the length of an arc of a circle.
  • Determine the areas of a sector and segment of a circle.
  • Compute the surface areas and volumes of three-dimensional objects.
  • Solve examples using trigonometric identities.
  • Solve problems involving heights and distances using trigonometry.

INDEX

  • Similarity: Pages 1 to 29
  • Pythagoras Theorem: Pages 30 to 46
  • Circle: Pages 47 to 90
  • Geometric Constructions: Pages 91 to 99
  • Co-ordinate Geometry: Pages 100 to 123
  • Trigonometry: Pages 124 to 139
  • Mensuration: Pages 140 to 163
  • Answers: Pages 164 to 168

Similarity of Triangles

  • Ratio of areas of two triangles, Basic proportionality theorem, Tests of similarity of triangles
  • Converse of basic proportionality theorem, Property of an angle bisector of a triangle, Property of areas of similar triangles
  • The ratio of the intercepts made on the transversals by three parallel lines

Ratio and Proportion

  • The numbers a and b are in the ratio m/n, which is written as: the numbers a and b are in proportion m:n.
  • This concept considers positive real numbers.
  • Lengths of line segments and figure areas are treated as positive real numbers
  • The area of a triangle is given by 1/2 * Base * Height.

Ratio of Areas of Two Triangles

  • The ratio of the areas of two triangles is equal to the ratio of the products of their bases and corresponding heights.
  • For two triangles, if the heights are equal, then the ratio of their areas is equal to the ratio of their corresponding bases
  • For two triangles, if the bases are equal, the the ratio of their areas is euqal to the ratio of their corresponding heights.

Basic Proportionality Theorem

  • If a line parallel to a side of a triangle intersects the remaining sides in two distinct points, then the line divides the sides in the same proportion

Converse of Basic Proportionality Theorem

  • If a line divides any two sides of a triangle in the same ratio, then the line is parallel to the third side

Property of the Angle Bisector

  • The bisector of an angle of a triangle divides the side opposite to the angle in the ratio of the remaining side

Angle Bisector Converse Theorem

  • If in ∆ABC, point D on side BC is such that AB/AC =BD/DC, then ray AD bisects ∠ BAC

Property of Three Parallel Lines and Their Transversals

  • The ratio of the intercepts made on a transversal by three parallel lines is equal to the ratio of the corresponding intercepts made on any other transversal by the same parallel lines.

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