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In right triangle ABC, with angle a=90, we have AB=6 and BC=10. Find Cos A

 Dec 11, 2018
 #1
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B

 

6          10

 

A           C

 

Cos A  =  AC / BC

 

By the Pythagorean Theorem

 

AC = sqrt ( BC^2 - AB^2)  = sqrt ( 10^2 - 6^2)  = sqrt (100 - 36)   = sqrt (64) = 8

 

So

 

Cos A =    8 / 10   =  4 / 5

 

 

 

cool cool cool

 Dec 11, 2018

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