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Learn properties of parallelograms such as rhombus, rectangle, and square. Find sides, angles, and diagonal lengths in special quadrilaterals.
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6.4 • EQ: What properties do we use to identify special types of parallelograms?
Parallelogram (review) • Both pairs of opposite sides are parallel • Both pairs of opposite sides are congruent • Both pairs of opposite angles are congruent • Consecutive angles are supplementary • Diagonals bisect each other
rhombus • a parallelogram with four congruent sides.
rhombus • a parallelogram with four congruent sides.
rectangle • A parallelogram with four right angles.
A parallelogram with four right angles. rectangle
A parallelogram with four right angles. rectangle
square • A parallelogram with four congruent sides and four right angles.
square • A parallelogram with four congruent sides and four right angles.
SOLUTION a. AD = BC = 5 andAB = DC = 8. b. By definition, a rectangle has four right angles, so mA = mB = mC = mD = 90°. Example 1 Use Properties of Special Parallelograms In the diagram, ABCDis a rectangle. a. Find ADand AB. b. Find mA, mB, mC, and mD.
Checkpoint 1. In the diagram, PQRSis a rhombus. Find QR, RS, and SP. ANSWER QR = 6,RS = 6, SP = 6 Use Properties of Special Parallelograms
Rhombus Corollary • If a quadrilateral has four congruent sides, then it is a rhombus.
Rectangle Corollary • If a quadrilateral has four right angles, then it is a rectangle.
Square Corollary • If a quadrilateral has four congruent sides and four right angles, then it is a square.
Checkpoint 2. rhombus ANSWER 3. square ANSWER Identify Special Quadrilaterals Use the information in the diagram to name the special quadrilateral.
Theorem 6.10 • The diagonals of a rhombus are perpendicular.
Example 3 Use Diagonals of a Rhombus ABCDis a rhombus. Find the value ofx. SOLUTION So, x = 90 – 60 = 30.
Theorem 6.11 • The diagonals of a rectangle are congruent.
Checkpoint 90 ANSWER 12 ANSWER 45 ANSWER Use Diagonals Find the value of x. 4. rhombusABCD 5. rectangleEFGH 6. squareJKLM