2tan−1x=sin−12x1−x22 \tan ^{-1} x=\sin ^{-1} \frac{2 x}{1-x^{2}}2tan−1x=sin−11−x22x
3tan−1x=tan−1x3−3x1−3x23 \tan ^{-1} x=\tan ^{-1} \frac{x^{3}-3 x}{1-3 x^{2}}3tan−1x=tan−11−3x2x3−3x
2cos−1x=cos−1(1−2x2)2 \cos ^{-1} x=\cos ^{-1}\left(1-2 x^{2}\right)2cos−1x=cos−1(1−2x2)
3sin−1x=sin−1(3x−4x3)3 \sin ^{-1} x=\sin ^{-1}\left(3 x-4 x^{3}\right)3sin−1x=sin−1(3x−4x3)
