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MHT CET · Maths · Differentiation

If \(y=\sin ^2\left(\cot ^{-1} \sqrt{\frac{1+x}{1-x}}\right)\), then \(\frac{\mathrm{d} y}{\mathrm{~d} x}\) has the value

  1. A \(\frac{-1}{2}\)
  2. B \(\frac{1}{2}\)
  3. C -1
  4. D 1
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{-1}{2}\)

Step-by-step Solution

Detailed explanation

\(y=\sin ^2\left(\cot ^{-1} \sqrt{\frac{1+x}{1-x}}\right)\)
Let \(\theta=\cot ^{-1} \sqrt{\frac{1+x}{1-x}}\)
\(\begin{array}{ll}
\therefore & \cot ^2 \theta=\frac{1+x}{1-x} \\
\therefore & 1+\cot ^2 \theta=\frac{2}{1-x} \\
\therefore & \sin ^2 \theta=\frac{1-x}{2} \\
\therefore & \theta=\sin ^{-1} \sqrt{\frac{1-x}{2}} \\
\therefore & y=\left[\sin \left(\sin ^{-1} \sqrt{\frac{1-x}{2}}\right)\right]^2 \\
\therefore & y=\frac{1-x}{2} \\
\therefore & \frac{\mathrm{~d} y}{\mathrm{~d} x}=\frac{-1}{2}
\end{array}\)