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Unformatted text preview: 95 Quadrilaterals in a Plane Continued
A) What do we need to know to conclude that a quadrilateral is a parallelogram? B) Theorem 919 a. Given a quadrilateral in which both pairs of opposite sides are congruent. Then the quadrilateral is a parallelogram i. C) Theorem 920 a. If two sides of a quadrilateral are parallel and congruent, then the quadrilateral is a parallelogram i. D) Theorem 921 a. If the diagonals of a quadrilateral bisect each other, then the quadrilateral is a parallelogram
i. E) Two others not in the book a. If both sets of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram i. b. If all sets of consecutive angles are supplementary in a quadrilateral, then the quadrilateral is a parallelogram F) The Midline Theorem a. The segment between the midpoints of two sides of a triangle is parallel to the third side and half as long
i. b. Proof 1) Given 1), D and E are the midpoints of and 2) EF = DE 3) EB = EC 4) 5) 6) 4) 2) Pointplotting Th. 5) 6) 7) 7) 8)AD = DB 8) 9) DB = FC 9) 10) AD = FC 10) 11) Quadrilateral ADFC is a parallelogram11) 11) 13) 14) AC = 2DE 15) 15) 12) 13) betweeness and APE 14) In the homework (number 21 and 23) A) B) The Quadrilateral Midpoint Theorem a. The quadrilateral formed by joining the midpoints of the consecutive sides of a quadrilateral is a parallelogram Isosceles Trapezoid Theorem a. The base angles of an isosceles trapezoid are congruent ...
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 Spring '09
 Johnson
 Algebra

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