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answer: 2 ... but how???

 

cos^2(20°) + cos^2(52°) + cos^2(38°) + cos^2(70°)

 

thanks to those who are helping everyone pass their class! your efforts are appreciated greatly :)

Guest Apr 25, 2017
 #1
avatar+87301 
+3

cos^2(20°) + cos^2(52°) + cos^2(38°) + cos^2(70°)

 

Note  cos (20°)  = sin (70”)

And   cos(52°)  =  sin (38°)

 

So.....we have

 

sin^2(70°)  + sin^2(38°)  + cos^2(38°) + cos^2(70°)     rearrange  as

 

[sin^2 (70°) + cos^2(70°)]  + [ sin^2(38°) + cos^2(38°) ]  =

 

             1                         +                   1     =                2

 

 

cool cool cool

CPhill  Apr 25, 2017

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