Q. 22

# Prove the following identities:

Proof:

Take LHS:

Identities used:

Therefore,

{ (a – b)(a + b) = a2 – b2;

(a + b)2 = a2 + b2 + 2ab &

(a – b)2 = a2 + b2 – 2ab}

{ cos2 x + sin2 x = 1 & cos 2x = cos2 x – sin2 x}

= 2 sec 2x

= RHS

Hence Proved

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