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MHT CET · Maths · Differentiation

If \(y=\tan ^{-1}(\sec x-\tan x)\), then \(\frac{d y}{d x}=\)

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

Answer & Solution

Correct Answer

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

Step-by-step Solution

Detailed explanation

\(y=\tan ^{-1}(\sec x-\tan x)=\tan ^{-1}\left(\frac{1-\sin x}{\cos x}\right)=\) \(\tan ^{-1}\left(\frac{\cos \frac{x}{2}-\sin \frac{x}{2}}{\cos \frac{x}{2}+\sin \frac{x}{2}}\right) \)
\( \Rightarrow y=\tan ^{-1}\left(\frac{1-\tan \frac{x}{2}}{1+\tan \frac{x}{2}}\right)=\tan ^{-1}\left(\tan \left(\frac{\pi}{4}-\frac{x}{2}\right)\right)\) \(=\frac{\pi}{4}-\frac{x}{2} \)
\( \Rightarrow \frac{d y}{d x}=\frac{-1}{2}\)