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Question: Answered & Verified by Expert
The point in the interval $[0,2 \pi]$, where $f(x)=e^x \sin x$ has maximum slope, is
MathematicsApplication of DerivativesWBJEEWBJEE 2010
Options:
  • A $\frac{\pi}{4}$
  • B $\frac{\pi}{2}$
  • C $\pi$
  • D $\frac{3 \pi}{2}$
Solution:
2693 Upvotes Verified Answer
The correct answer is: $\frac{\pi}{2}$
Hints: $f^{\prime}(x)=e^x(\sin x+\cos x)$
$$
\begin{aligned}
& f^{\prime \prime}(x)=e^x(\sin x+\cos x+\cos x-\sin x) \Rightarrow f^{\prime \prime}(x)=e^x \cos x=0 \\
& \Rightarrow x=\frac{\pi}{2}
\end{aligned}
$$

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