Prove that: `3cos^(-1)x=cos^(-1)(4x^3-3x), x in [1/2,1]`

1.	Prove that: `3cos^(-1)x=cos^(-1)(4x^3-3x), x in [1/2,1]`
Answer» Let `cos^(-1)x=theta` `RHS=cos^(-1)(4x^(3)-3x)` `=cos^(-1)(4cos^(3)theta- 3 cos theta)` `= cos^(-1)(cos 3 theta)` `=3theta=3 cos^(-1)x` = LHS Hence Proved.

Discussion

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