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is equal to

We need to find the value of:


Take cosine on both sides, we get

Using property of inverse trigonometry,

cos(cos-1 A) = A

We have the value of cos x, let us find the value of sin x.

By trigonometric identity,

sin2 x + cos2 x = 1

sin2 x = 1 – cos2 x

Putting ,


Using the trigonometric identity,

sin 2x = 2 sin x cos x

Putting the value of and ,