Q10 of 30 Page 2

Prove the following:

Let x = cos θ

Then, Cos-1 = θ


Now, R.H.S. = cos-1(4x3 - 3x)


= cos-1(4cos3θ - 3cos θ)


= cos-1(cos3θ)


= 3θ


= 3cos-1x


= L.H.S.


Hence Proved

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