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CUET · MATHS · PYQ PAPER 2025

If \(f(x)=\left\{\begin{array}{ll}\frac{1-\tan x}{4 x-\pi} & x \neq \frac{\pi}{4} \\ k & x=\frac{\pi}{4}\end{array}\right.\) is continuous at \(x=\frac{\pi}{4}\), then the value of \(k\) is

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

Correct Answer

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

Step-by-step Solution

Detailed explanation

\(k = \lim_{x \to \frac{\pi}{4}} \frac{1-\tan x}{4x-\pi}\) \(k = \lim_{x \to \frac{\pi}{4}} \frac{\frac{d}{dx}(1-\tan x)}{\frac{d}{dx}(4x-\pi)}\) (L'Hôpital's Rule) \(k = \lim_{x \to \frac{\pi}{4}} \frac{-\sec^2 x}{4}\) \(k = \frac{-\sec^2(\frac{\pi}{4})}{4}\)…
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