Q9 of 123 Page 9

Prove the following identities:


Proof:


Take LHS:



Identities used:


cos 2x = 2 cos2 x – 1


⇒ 2 cos2 x = 1 + cos 2x



Therefore,






{∵ cos (π – θ) = - cos θ, cos (π + θ) = - cos θ & cos(2π – θ) = cos θ}




= 2


= RHS


Hence Proved


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