Parallelograms: Properties and Conditions
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Questions and Answers

In an isosceles trapezoid $ABCD$, where $AB$ and $CD$ are the bases, which of the following statements is NOT necessarily true?

  • The diagonals $AC$ and $BD$ are congruent.
  • Angles $∠ABC$ and $∠BAD$ are congruent.
  • Angles $∠ADC$ and $∠BCD$ are congruent.
  • Angles $∠ABC$ and $∠BCD$ are supplementary. (correct)
  • Given a kite $EFGH$ where $EG$ is the longer diagonal and $FH$ is the shorter diagonal. If $∠FEH = 50°$, what is the measure of $∠FGH$?

  • 50° (correct)
  • Cannot be determined without additional information.
  • 130°
  • 80°
  • A trapezoid has bases of length 10 and 14. What is the length of its median?

  • 24
  • 14
  • 10
  • 12 (correct)
  • Quadrilateral $PQRS$ has diagonals that are perpendicular bisectors of each other. Which of the following classifications is $PQRS$ guaranteed to be?

    <p>Rhombus (C)</p> Signup and view all the answers

    Two similar triangles, $ΔABC$ and $ΔDEF$, have corresponding sides $AB = 6$ and $DE = 9$. If the area of $ΔABC$ is 24 square units, what is the area of $ΔDEF$?

    <p>54 square units (C)</p> Signup and view all the answers

    In parallelogram $ABCD$, diagonals $AC$ and $BD$ intersect at point $E$. If $AE = 3x + 2$ and $EC = 7x - 6$, what is the length of $AC$?

    <p>28 (C)</p> Signup and view all the answers

    Which of the following conditions is sufficient to prove that a quadrilateral is a parallelogram?

    <p>One pair of opposite sides is both congruent and parallel. (D)</p> Signup and view all the answers

    In rectangle $PQRS$, $PR = 5x - 3$ and $QS = 3x + 5$. What is the length of $PR$?

    <p>17 (B)</p> Signup and view all the answers

    Which property is unique to rhombuses compared to all other parallelograms?

    <p>All sides are congruent. (C)</p> Signup and view all the answers

    In rhombus $WXYZ$, if $\angle WXY = 60^{\circ}$, what is the measure of $\angle WZY$?

    <p>$60^{\circ}$ (D)</p> Signup and view all the answers

    Three lines intersect at the same point. What is this configuration called?

    <p>Concurrent lines (D)</p> Signup and view all the answers

    If the consecutive angles of a quadrilateral are supplementary, which type of quadrilateral can it be definitively classified as?

    <p>Parallelogram (C)</p> Signup and view all the answers

    Which of the following statements is always true for a square?

    <p>It is both equiangular and equilateral. (A)</p> Signup and view all the answers

    Flashcards

    Properties of a square

    All angles are right; diagonals bisect and are congruent.

    Median of a trapezoid

    A segment joining midpoints of non-parallel sides, half the sum of the bases.

    Isosceles trapezoid

    A trapezoid with congruent legs and base angles; diagonals are also congruent.

    Properties of a kite

    Two pairs of consecutive sides are congruent; one diagonal bisects the other.

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    Similar figures

    Shapes with proportional sides and congruent angles.

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    Parallelogram

    A quadrilateral with opposite sides that are parallel and congruent.

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    Properties of Parallelograms

    Includes opposite sides congruent, opposite angles congruent, diagonals bisect each other, and consecutive angles supplementary.

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    Conditions for Parallelogram

    Conditions include: both pairs of opposite sides congruent, one pair of opposite sides congruent and parallel, both pairs of opposite angles congruent, and diagonals bisect each other.

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    Rectangle

    A parallelogram with four right angles and opposite sides that are congruent.

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    Rhombus

    A parallelogram with all sides congruent and opposite angles congruent.

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    Square

    A parallelogram that is both a rectangle and a rhombus with equal sides and angles.

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    Diagonals of Parallelogram

    Diagonals bisect each other and divide the parallelogram into two congruent triangles.

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    Supplementary Angles

    Angles whose measures add up to 180 degrees, key property for parallelograms.

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    Study Notes

    Parallelograms

    • Parallelograms are quadrilaterals with opposite sides parallel.
    • Intersecting lines share a common point.
    • Concurrent lines share a common point.
    • Perpendicular lines intersect at a right angle.
    • Transversal lines intersect two or more lines at distinct points.

    Properties of Parallelograms

    • Opposite sides are parallel and congruent.
    • Opposite angles are congruent.
    • Consecutive angles are supplementary (add up to 180 degrees).
    • Diagonals bisect each other.
    • Each diagonal divides the parallelogram into two congruent triangles.

    Conditions for a Quadrilateral to be a Parallelogram

    • Condition 1: If both pairs of opposite sides are congruent, then the quadrilateral is a parallelogram.
    • Condition 2: If one pair of opposite sides is congruent and parallel, then the quadrilateral is a parallelogram.
    • Condition 3: If both pairs of opposite angles are congruent, then the quadrilateral is a parallelogram.
    • Condition 4: If consecutive angles are supplementary, then the quadrilateral is a parallelogram.
    • Condition 5: If the diagonals bisect each other, then the quadrilateral is a parallelogram.
    • Condition 6: If each diagonal forms two congruent triangles, then the quadrilateral is a parallelogram.

    Rectangles

    • A parallelogram with four right angles.
    • Equiangular but not necessarily equilateral.
    • Opposite sides are parallel and congruent.
    • All angles are congruent and are right angles.
    • Consecutive angles are supplementary.
    • Diagonals bisect each other and are congruent.
    • Each diagonal divides the rectangle into two congruent triangles.

    Rhombus

    • A quadrilateral with four congruent sides.
    • Equiangular but not equilateral.
    • Opposite sides are parallel and congruent.
    • All sides are congruent.
    • Opposite angles are congruent.
    • Consecutive angles are supplementary.
    • Each diagonal bisects a pair of opposite angles.
    • Each diagonal is a perpendicular bisector of the other diagonal.
    • Each diagonal divides the rhombus into two congruent triangles.
    • The diagonals of a rhombus are perpendicular.

    Square

    • A quadrilateral with four congruent sides and four congruent angles (right angles).
    • All sides are parallel and congruent.
    • All sides are congruent.
    • All angles are congruent and are right angles.
    • Opposite angles are congruent and supplementary.
    • Consecutive angles are supplementary and congruent.
    • Diagonals are congruent and bisect opposite angles.
    • Each diagonal is a perpendicular bisector of the other diagonal.
    • Each diagonal divides the square into two congruent triangles.

    Trapezoid

    • A quadrilateral with exactly one pair of parallel sides.
    • The parallel sides are called bases.
    • The non-parallel sides are called legs.
    • The median of a trapezoid is a segment connecting the midpoints of the legs. It's parallel to the bases and its length is half the sum of the lengths of the bases.
    • Isosceles Trapezoid: A trapezoid in which the legs are congruent. Base angles are congruent and diagonals are congruent.

    Kite

    • A quadrilateral with two distinct pairs of consecutive congruent sides.
    • Only one pair of opposite angles is congruent.
    • One diagonal bisects the other.
    • The diagonals are perpendicular.
    • The area of a kite is half the product of the lengths of its diagonals.

    Similar Figures

    • Figures with the same shape but not necessarily the same size.
    • Corresponding sides are proportional.
    • Corresponding angles are congruent.

    Congruent Figures

    • Figures with the same shape and size.
    • Corresponding sides and angles are congruent.

    Basic Proportionality Theorem (BPT)

    • If a line is drawn parallel to one side of a triangle and intersects the other two sides in distinct points, then it divides the sides proportionally.

    Right Triangle Similarity Theorem

    • If the altitude is drawn to the hypotenuse of a right triangle, then the two triangles formed are similar to each other and to the original right triangle.

    Geometric Mean Theorem

    • In a right triangle, the altitude to the hypotenuse divides the hypotenuse in two segments, and the altitude is the geometric mean of the segments. The length of a leg is the geometric mean of the hypotenuse and the adjacent segment.

    Special Right Triangles

    • 45-45-90 Triangles: The hypotenuse is √2 times the length of a leg.
    • 30-60-90 Triangles: The hypotenuse is twice the length of the shorter leg, and the longer leg is √3 times the shorter leg.

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    Explore the properties of parallelograms, including congruent sides and angles. Understand the conditions that define a quadrilateral as a parallelogram, such as congruent and parallel opposite sides. Learn about transversals, intersecting, concurrent, & perpendicular lines.

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