Prove: Cos^2a + Cos ^2(a+ 120)+ Cos^2(a-120) = 3/2
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vamshi banka

Cos 2A = 2Cos2(A) – 1


Cos 2A + 1 = 2 Cos 2 ( A )  


(1 + Cos 2A)  /2 = Cos 2A


i.e  Cos 2A = (1 + Cos 2A)/2




1 + Cos2 A( -1/2  ) + Cos2 A


1- ( 2 Cos 2A -1) (  1/2  ) + Cos2A


1 – Cos2A + (  1/2  ) + Cos2 A


= 3/2


 

6 days ago
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