DiB_2021

যদি f(x)=tan1xf(x)=\tan ^{-1} x হলে—i. 2f(x)=tan12x1x22 f(x)=\tan ^{-1} \frac{2 x}{1-x^{2}}ii. 2f(x)=sin12x1x22 f(x)=\sin ^{-1} \frac{2 x}{1-x^{2}}iii. 2f(x)=cos11x21+x22 f(x)=\cos ^{-1} \frac{1-x^{2}}{1+x^{2}}নিচের কোনটি সঠিক?

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