If $\int e^x\left(\frac{1-\sin x}{1-\cos x}\right) d x=f(x)+$ constant, then $f(x)$ is equal to

If $\int e^x\left(\frac{1-\sin x}{1-\cos x}\right) d x=f(x)+$ constant, then $f(x)$ is equal to
  1. $e^x \cot \left(\frac{x}{2}\right)+c$
  2. $e^{-x} \cot \left(\frac{x}{2}\right)+c$
  3. $-e^x \cot \left(\frac{x}{2}\right)+c$
  4. $-e^{-x} \cot \left(\frac{x}{2}\right)+c$

Solution

$\begin{aligned} & \int e^x\left(\frac{1-\sin x}{1-\cos x}\right) d x \\ & \quad=\int e^x\left(\frac{1-2 \sin \frac{x}{2} \cos \frac{x}{2}}{2 \sin ^2 \frac{x}{2}}\right) d x \\ & \quad=\frac{1}{2} \int e^x\left(\operatorname{cosec}^2 \frac{x}{2}\right) d x-\int e^x \cot \frac{x}{2} d x \\ & \quad=\frac{1}{2}\left[-e^x \cot \frac{x}{2} \cdot 2+\int e^x \cot \frac{x}{2} 2 d x\right] \\ & \quad=-e^x \cot \frac{x}{2}+c\end{aligned}$

Asked in: MHT CET Full Test 7

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