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AMSCO'S Geometry. New York - Rye High School

AMSCO'S Geometry. New York - Rye High School

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The Trapezoid 407The slopes of BC and DA are equal. Therefore, BC and DA are parallel.The slopes of AB and CD are not equal. Therefore, AB and CD are not parallel.Because quadrilateral ABCD has only one pair of parallel sides, it isa trapezoid.EXAMPLE 2SolutionIn quadrilateral ABCD,mA 105, mB 75, and mC 75.a. Is ABCD a parallelogram? Justify your answer.b. Is ABCD a trapezoid? Justify your answer.c. Is ABCD an isosceles trapezoid? Justify your answer.d. If AB x, BC 2x 1, CD 3x 8, and DA x 1,find the measure of each side of the quadrilateral.a. One pair of opposite angles of ABCD are A and C.Since these angles are not congruent, the quadrilateral isnot a parallelogram. The quadrilateral does not have twopairs of parallel sides.b. A and B are interior angles on the same side of transversal AB andthey are supplementary. Therefore, AD and BC are parallel. The quadrilateralhas only one pair of parallel sides and is therefore a trapezoid.c. Because B and C are congruent base angles of the trapezoid, thetrapezoid is isosceles.d. The congruent legs of the trapezoid are AB and CD.AB CDx 3x 82x 8x 4D105°A75°C75°BAB x BC 2x 1 CD 3x 8 DA x 1 4 2(4) 1 3(4) 8 4 1 8 1 12 8 5 7 4

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