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AP EAMCET · Maths · Indefinite Integration

In \(I_n=\int \frac{\sin n x}{\sin x} d x\) for \(n=1,2,3, \ldots\), then \(I_6=\)

  1. A \(\frac{3}{5} \sin 3 x+\frac{8}{5} \sin ^5 x-\sin x+c\)
  2. B \(\frac{2}{5} \sin 5 x-\frac{5}{3} \sin ^3 x-2 \sin x+c\)
  3. C \(\frac{2}{3} \sin 5 x-\frac{8}{3} \sin ^5 x+4 \sin x+c\)
  4. D \(\frac{2}{5} \sin 5 x-\frac{8}{5} \sin ^3 x+4 \sin x+c\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{2}{5} \sin 5 x-\frac{8}{5} \sin ^3 x+4 \sin x+c\)

Step-by-step Solution

Detailed explanation

Subtracting Eq. (ii) from Eq. (i), we get \[ \begin{aligned} & I_n-I_{n-2}=\int \frac{\{\sin n x-\sin (n-2) x\}}{\sin x} d x \\ & =\int \frac{2 \cos (n-1) x \sin x}{\sin x} d x=\int 2 \cos (n-1) x d x \\ & =\frac{2 \sin (n-1) x}{(n-1)} \end{aligned} \]…