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Parallelograms & Tests for Parallelograms. Notes 22 – Sections 6.2 & 6.3. Essential Learnings. Students will understand and be able to recognize and apply properties of parallelograms.
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Parallelograms &Tests for Parallelograms Notes 22 – Sections 6.2 & 6.3
Essential Learnings • Students will understand and be able to recognize and apply properties of parallelograms. • Students will understand and be able to recognize the conditions that ensure a quadrilateral is a parallelogram.
Properties of Parallelograms • If a quadrilateral is a parallelogram, then its opposite sides are congruent.
Properties of Parallelograms • If a quadrilateral is a parallelogram, then its opposite angles are congruent.
Properties of Parallelograms • If a quadrilateral is a parallelogram, then its consecutive angles are supplementary. mA + mB = 180 mB + mC = 180 mC + mD = 180 mD + mA = 180 B A C D
Properties of Parallelograms • If a parallelogram has one right angle, then it has four right angles.
Example 1 In parallelogram ABCD, suppose m∠B = 32, CD = 80 inches, and BC = 15 inches. Find each measure. AD = m∠C = m∠D = A B D C
Diagonals of Parallelograms • If a quadrilateral is a parallelogram, then its diagonals bisect each other.
Diagonals of Parallelograms • If a quadrilateral is a parallelogram, then each diagonal separates the parallelogram into two congruent triangles.
Example 2 If JKLM is a parallelogram, find the value of the indicated variable. x = y= z = 2zº 4x J K 7y+3 8y 40º 18º L 18 M
Conditions for Parallelograms • If both pairs of opposite sides of a quadrilateral are congruent, then the quadrilateral is a parallelogram. A B ABDC ADBC then ABCD is a parallelogram. D C
Conditions for Parallelograms • If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram. W X mWmY mZmX then WXYZ is a paralellogram. Z Y
Conditions for Parallelograms • If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram.
Conditions for Parallelograms • If one pair of opposite sides of a quadrilateral is both parallel and congruent, then the quadrilateral is a parallelogram.
Example 3 Determine whether the quadrilateral is a parallelogram. Justify your answer. 100º 14 14 80º
Example 4 Determine whether the quadrilateral is a parallelogram. Justify your answer. 71º 70º
Example 5 Find x and y so that the quadrilateral is a parallelogram. 4x-1 3(y+1) 4y-2 3(x+2)
Example 6 Find x and y so that the quadrilateral is a parallelogram. -2x+6 -4y-2 x+12 y+23
Assignment p. 403: 9 - 12, 15 - 20, 31 - 36 p. 414: 9 - 14, 18 – 23