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avatar+315 

Trig

 Apr 25, 2019
 #1
avatar+106535 
+2

Let a/2  = B      so a  = 2B

 

And we have the identity that

 

cos 2B  = 2cos^2 B - 1        add 1 to both sides

 

cos 2B + 1  = 2 cos^2 B        divide both sides by 2

 

cos 2B + 1

________    =  cos^2 B       take both roots

     2

 

 

±√ [ ( cos 2B + 1 ) / 2 ]  = cos B

 

So.....

 

True  !!!

 

 

cool cool cool 

 Apr 25, 2019
 #2
avatar+315 
+1

Thank you, CPhill! smiley

Cupcake  Apr 25, 2019

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