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In the triangle ABC, sin A = 4/5. Find cos B.

 

 

 Jun 8, 2019
edited by Aopshelp  Jun 8, 2019
 #1
avatar+111321 
+3

Draw altitude CM

 

Then CM  must  = 8    because  sin A  = CM / AC  =   8/10   = 4/5

 

Using the Pythagorean Theorem   BM  =  sqrt  (BC^2 - CM^2)  = sqrt ( 17^2 - 8^2)  = sqrt ( 289 - 64) =

sqrt ( 225)  =  15

 

And cos B  =   BM / BC    =   15/ 17

 

cool cool cool 

 Jun 8, 2019
 #2
avatar+57 
+3

THANK YOU SO MUCH BROHAM

cool

Aopshelp  Jun 8, 2019
 #3
avatar+111321 
+2

OK....but.....I suspect hectictar might have gotten the same answer  !!!

 

I just beat her to the punch   ....LOL!!!!

 

cool cool cool

CPhill  Jun 8, 2019
 #4
avatar+8945 
+3

Hahaha!! laughlaughlaugh

hectictar  Jun 8, 2019

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