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Learn about the properties and characteristics of parallelograms, specifically rectangles, rhombuses, and squares. Understand their definitions, theorems about diagonals, and examples of trapezoids and kites.
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Do Now: List all you know about the following parallelograms. 1.) Rectangle 2.) Rhombus 3.) Square
Geometry 8.4: Properties of Rhombuses, Rectangles, and Squares 8.5: e Properties of Trapezoids and Kites
Rectangles • Parallelogram with 4 right angles
Rhombus • Parallelogram with four congruent sides.
Square • A square is a parallelogram with four congruent sides and four right angles. • A square is a rhombus and a rectangle.
Theorems about Diagonals • Diagonals of a rhombus are perpendicular (also true for a square- remember a square is a rhombus.)
Theorems about Diagonals • Diagonals of a rhombus bisect the opposite angles (also true for a square - remember a square is a rhombus.)
Theorems about Diagonals • Diagonals of a rectangle are congruent (also true for a square- remember a square is a rectangle.)
Trapezoids • A trapezoid is a quadrilateral with exactly one pair of parallel sides. (not parallelogram) • The parallel sides are called bases. The other two sides are called legs. • A trapezoid has two pairs of base angles. base A B One pair of base Angles: A & B. Another pair: D and C. leg leg C D base
Isosceles Trapezoids • If the legs of a trapezoid are congruent, then the trapezoid is an isosceles trapezoid. • Theorem 8.14: If a trapezoid is isosceles, then each pair of base angles is congruent. A B D C
Theorem 8.15 • If a trapezoid has a pair of congruent base angles, then it is an isosceles trapezoid. A B D C ABCD is an isosceles trapezoid. (AD is congruent to BC).
Theorem 8.16 • A trapezoid is isosceles if and only if its diagonals are congruent. A B D C ABCD is an isosceles trapezoid if and only if .
Midsegment of a Trapezoid • Midsegment connects the midpoints of the legs. • Theorem 8.17: The midsegment of a trapezoid is parallel to each base and its length is one half the sum of the lengths of the bases. (average) A B Midsegment M N D C
Examples Find the length of the other base.
Kites • A kite is a quadrilateral that has two pairs of consecutive congruent sides, but opposite sides are not congruent. (not parallelogram)
Kites • Theorem 8.18: If a quadrilateral is a kite, then its diagonals are perpendicular. • Theorem 8.19: If a quadrilateral is a kite, then exactly one pair of opposite angles are congruent.