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What is the largest angle measure in a triangle with sides of lengths 3, 8, and 7? 

 Jun 25, 2022
 #1
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The largest  angle is opposite the longest side

 

Let A  be that angle

 

Using the Law of Cosines

 

 

8^2    = 3^2 + 7^2  - 2 (3)(8) cos A

 

cos A   =    [  8^2 - 3^2 - 7^2 ] / [ -2 * 3 * 8 ] 

 

 

arccos  [ ( 8^2 - 3^2 - 7^2 )  / ( -2 * 3 * 8 )  ]   = A   =    97.18°  

 

 

 

cool cool cool

 Jun 25, 2022

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