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