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Showing quadrilaterals are parallelograms. Bell Ringer. Tell whether the quadrilateral is a parallelogram. Explain your reasoning. SOLUTION. The quadrilateral is not a parallelogram. It has two pairs of congruent sides, but opposite sides are not congruent. Example 1. Use Opposite Sides.
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Tell whether the quadrilateral is a parallelogram. Explain your reasoning. SOLUTION The quadrilateral is not a parallelogram. It has two pairs of congruent sides, but opposite sides are not congruent. Example 1 Use Opposite Sides
Tell whether the quadrilateral is a parallelogram. Explain your reasoning. SOLUTION The quadrilateral is a parallelogram because both pairs of opposite angles are congruent. Example 2 Use Opposite Angles
Tell whether the quadrilateral is a parallelogram. Explain your reasoning. Now You Try 1. Yes; both pairs of opposite sides are congruent. ANSWER 2. No; opposite angles are not congruent. ANSWER 3. In quadrilateral WXYZ, WX =15, YZ =20, XY =15, and ZW =20. Is WXYZa parallelogram? Explain your reasoning. No; opposite sides are not congruent. ANSWER
a. b. c. SOLUTION a. Uis supplementary to Tand V (85° + 95° = 180°). So, by Theorem 6.8, TUVWis a parallelogram. b. Gis supplementary to F (55° + 125° = 180°), but Gis not supplementary to H (55° + 120° ≠ 180°). So, EFGHis not a parallelogram. Tell whether the quadrilateral is a parallelogram. Explain your reasoning. Example 3
c. Dis supplementary to C(90° + 90° = 180°), but you are not given any information about Aor B. Therefore, you cannot conclude that ABCDis a parallelogram. Example 3 Use Consecutive Angles
Tell whether the quadrilateral is a parallelogram. Explain your reasoning. a. b. SOLUTION a. The diagonals of JKLMbisect each other. So, by Theorem 6.9, JKLMis a parallelogram. b. The diagonals of PQRSdo not bisect each other. So, PQRSis not a parallelogram. Example 4
Tell whether the quadrilateral is a parallelogram. Explain your reasoning. Now You Try 4. No; opposite angles are not congruent (or consecutive angles are not supplementary). ANSWER Yes; one angle is supplementary to both of its consecutive angles. ANSWER 5.
Tell whether the quadrilateral is a parallelogram. Explain your reasoning. Now You Try 6. Yes; the diagonals bisect each other. ANSWER 7. No; the diagonals do not bisect each other. ANSWER
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