1.

Prove the identity: sin 2x/(1 – cos 2x) = cot x

Answer»

Let us consider the LHS

sin 2x/(1 – cos 2x)

As we know that cos 2x = 1 – 2 sin2 x

Sin 2x = 2 sin x cos x

Therefore,

sin 2x/(1 – cos 2x) = (2 sin x cos x)/(1 – (1 – 2sin2 x))

= (2 sin x cos x)/(1 – 1 + 2sin2 x)]

= [2 sin x cos x/2 sin2 x]

= cos x/sin x

= cot x

= RHS

Thus proved.



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