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Math Challenge IV Fall Week 1 HW

 
 
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Math Challenge IV Fall Week 1 HW
by Derek Dong - Friday, September 21, 2018, 5:01 PM
 

I've spent way too long on Example 6, and have only completed the first part.

So I have: DE=DF implies AEDF is cyclic, and I am trying to prove angle EDF is acute for part b, but I have not found a helpful angle chase. Is this approach correct, and if so, what should I be looking for in my angle chase?

 
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Re: Math Challenge IV Fall Week 1 HW
by Areteem Professor - Friday, September 21, 2018, 8:46 PM
 

To prove an angle is greater than 90 degrees, you can use the Law of Cosines.  Also the equality in the first part can be applied.


 
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