$\int_0^{\frac{\pi}{2}} \frac{\sin x-\cos x}{1-\sin x \cos x} d x=$
$\int_0^{\frac{\pi}{2}} \frac{\sin x-\cos x}{1-\sin x \cos x} d x=$
- $\frac{\pi}{4}$
- $\frac{2}{\pi}$
- 0
- $\frac{\pi}{2}$
Solution
Let $I=\int_0^{\pi / 2} \frac{\sin x-\cos x}{1-\sin x \cos x} d x$
$\begin{aligned}
& \therefore I=\int_0^{\frac{\pi}{2}} \frac{\sin \left(\frac{\pi}{2}-x\right)-\cos \left(\frac{\pi}{2}-x\right)}{1-\sin \left(\frac{\pi}{2}-x\right) \cos \left(\frac{\pi}{2}-x\right)} d x \\
& =\int_0^{\pi / 2} \frac{\cos x-\sin x}{1-\cos x \sin x} d x
\end{aligned}$
Eq. (1) $+(2)$ gives
$2 \mathrm{I}=\int_0^{\frac{\pi}{2}} 0 \mathrm{dx} \Rightarrow \mathrm{I}=0$
Asked in: MHT CET 2021 (21 Sep Shift 1)
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