If $\int \frac{(\cos x-\sin x)}{8-\sin 2 x} d x=\frac{1}{p} \log \left[\frac{3+\sin x+\cos x}{3-\sin x-\cos…

If $\int \frac{(\cos x-\sin x)}{8-\sin 2 x} d x=\frac{1}{p} \log \left[\frac{3+\sin x+\cos x}{3-\sin x-\cos x}\right]+c$, then $\mathrm{p}=($ Where $\mathrm{c}$ is a constant of integration)
  1. 12
  2. $\frac{1}{6}$
  3. 6
  4. 3

Solution

$\begin{aligned} & \text { Let } I=\int \frac{\cos x-\sin x}{8-\sin 2 x} d x \\ & =\int \frac{\cos x-\sin x}{9-1-\sin 2 x} d x=\int \frac{\cos x-\sin x}{9-(1+\sin 2 x)} d x \\ & =\int \frac{\cos x-\sin x}{(3)^2-(\sin x+\cos x)^2} d x \end{aligned}$ Put $\sin x+\cos x=t \Rightarrow(\cos x-\sin x) d x=d t$ $\begin{aligned} & \therefore I=\int \frac{d t}{(3)^2-(t)^2} d x=\frac{1}{3(2)} \log \left|\frac{3+t}{3-t}\right|+c \\ & =\frac{1}{6} \log \left|\frac{3+\sin x+\cos x}{3-\sin x-\cos x}\right|+c \Rightarrow p=6 \end{aligned}$

Asked in: MHT CET 2021 (23 Sep Shift 1)

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