Theorem

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# Theorem - PowerPoint PPT Presentation

Theorem. A quadrilateral is a parallelogram if and only if the diagonals bisect each other. . The diagonals bisect each other. Line segment DE is congruent to line segment EB &amp; line segment AE is congruent to line segment EC. . What am I trying to prove?. ABCD is a parallelogram.

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## PowerPoint Slideshow about 'Theorem' - yahto

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Presentation Transcript

### Theorem

A quadrilateral is a parallelogram if and only if the diagonals bisect each other.

The diagonals bisect each other. Line segment DE is congruent to line segment EB & line segment AE is congruent to line segment EC. What am I trying to prove?
I have triangles. If I can prove that triangle ABE and triangle DEC are congruent then I can show that line segment DE is congruent to line segment EB & line segment AE is congruent to line segment EC because of CPCTC. First I have to show that the two triangles are congruent. What do I know?
Since I know that ABCD is a parallelogram then I can say that AB is parallel to DC. I can use the theorem about parallel lines. How do I do that?
I can say that these two triangles are congruent because of ASA. I showed all of the requirements. Because I showed that triangle ABE and triangle DEC are congruent, I can state that DE is congruent to EB & AE is congruent to EC. Thus the two diagonal bisect each other. Conclusion