$\int \frac{\cos x-\sin x}{5+\sin (2 x)} d x=$

$\int \frac{\cos x-\sin x}{5+\sin (2 x)} d x=$
  1. $\frac{1}{2} \cot ^{-1}\left[\frac{1}{2}(\sin x+\cos x)\right]+c$
  2. $\frac{1}{2} \tan ^{-1}\left[\frac{1}{2}(\sin x+\cos x)\right]+c$
  3. $\frac{1}{2} \sin ^{-1}\left[\frac{1}{2}(\sin x+\cos x)\right]+c$
  4. $\frac{1}{2} \cos ^{-1}\left[\frac{1}{2}(\sin x+\cos x)\right]+c$

Solution

$ \text { } \begin{aligned} I & =\int \frac{\cos x-\sin x}{5+\sin 2 x} d x \\ & =\int \frac{\cos x-\sin x}{4+(\sin x+\cos x)^2} d x \end{aligned} $ Let $\sin x+\cos x=t \Rightarrow(\cos x-\sin x) d x=d t$ $ \begin{aligned} \therefore \quad I & =\int \frac{d t}{4+t^2}=\frac{1}{2} \tan ^{-1}\left(\frac{t}{2}\right)+C \\ & =\frac{1}{2} \tan ^{-1}\left(\frac{\sin x+\cos x}{2}\right)+C \end{aligned} $

Asked in: AP EAMCET 2020 (22 Sep Shift 1)

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