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Question: Answered & Verified by Expert
Let \( f(x)=\left\{\begin{array}{cc}\frac{1+\cos x}{(\pi-x)^{2}} \cdot \frac{\sin ^{2} x}{\log \left(1+\pi^{2}-2 \pi x+x^{2}\right)} & , \quad x \neq \pi \\ k & , \quad x=\pi\end{array}\right. \). If \( f(x) \) is continuous functions at \( x=\pi \), then \( k \) is equal to
MathematicsContinuity and DifferentiabilityJEE Main
Options:
  • A \( \frac{1}{4} \)
  • B \( \frac{1}{2} \)
  • C \( \frac{-1}{2} \)
  • D \( -\frac{1}{4} \)
Solution:
1365 Upvotes Verified Answer
The correct answer is: \( \frac{1}{2} \)
The given function is
f x = { 1 + cos x π - x 2 · sin 2 x log 1 + π 2 - 2 π x + x 2 , x π k , x = π
Since, f(x) continuous at x = π.
∴                      lim x π f x = f π
⇒               lim h 0 f π + h = k lim h 0 1 + cos π + h π - π - h 2 ·
                                     sin 2 π + h log 1 + π 2 - 2 π π + h + π + h 2 = k
⇒                  lim h 0 1 - cos h π 2 × sin 2 h log 1 + h 2 = k
⇒             lim h 0 1 2 sin h/2 h/2 2 · h 2 log 1 + h 2 · sin h h 2 = k
⇒                                  1 2 = k

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