How do I prove that: 2sin^-1(x)=cos^-1 * (1-2x^2) x>=0
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Originally Posted by Asuhuman18 How do I prove that: 2sin^-1(x)=cos^-1 * (1-2x^2) x>=0 Try proving that $\displaystyle \cos(2\sin^{-1}x)=1-2x^2$. This identity will help: $\displaystyle \cos2\theta=1-\sin^2\theta$
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