See complete Problem 71

Cyclic Quadrilateral, Angles. Level: High School, SAT Prep, College geometry

Post your solutions or ideas in the comments.

## Monday, May 19, 2008

### Elearn Geometry Problem 71

Labels:
angle,
circle,
cyclic quadrilateral

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ABCD is a cyclic quadrilateral therefore angle beta and angle BCD are supplimentary. So beta + BCD = 180 degrees. Also, alpha + angle BCD = 180 degrees because they lie on a straight line. therefore alpha equals beta.

ReplyDeleteCan anyone tell me if this is right?

Yes, it is right. Q.E.D.

ReplyDeleteVideo-solution

ReplyDeletehttp://www.youtube.com/watch?v=D-DFhH8XYgM

Note that the reciprocal is true.

β+∡BCD=180°

ReplyDeleteβ=180°-∡BCD

α+∡BCD=180°

α=180°-∡BCD

α=β

β+∡BCD=180°

ReplyDeleteβ=180°-∡BCD

α+∡BCD=180°

α=180°-∡BCD

α=β