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Problem 8.15

 
 
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Problem 8.15
by Jimmy Muren - Wednesday, November 1, 2017, 9:10 PM
 

Suppose a trapezoid ABCD with base AD is inscribed in a circle. If AB=4, then what is CD?

I made the trapezoid, and I remember that if we draw diagonals AC and BD and call the intersection O, then triangles AOB and COD have the same area, but I don't know how to go on from there, or maybe I am using the wrong strategy?

 
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Re: Problem 8.15
by John Lensmire - Friday, November 3, 2017, 3:18 PM
 

Often a good thing to think about when you are stuck is the information the problem gives you. We know basically:

  1. We have a trapezoid $ABCD$ with base $AD$.
  2. $AB=4$.
  3. The trapezoid is inscribed in a circle, that is, $ABCD$ is a cyclic quadrilateral.

Keeping in mind all of this information should help get you started!

Let us know if you have more questions.

 
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