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Need solution for RD Sharma Maths Class 12 Chapter 18 Indefinite Integrals Excercise 18.7 Question 3

Answers (1)

Answer:

             =\frac{1}{2}\left[\frac{\sin (m+n) x}{m+n}+\frac{\sin (m-n) x}{m-n}\right]+c

Hint:

             2\cos A\cos B=\cos\left ( A+B \right )+\cos\left ( A-B \right )

Given:

              \cos mx\cos nx dx,m\neq n

Explanation:

\begin{aligned} &\int(\cos m x \cos n x) d x=\frac{1}{2} \int[\cos (m+n) x+\cos (m-n) x] d x \\ &=\frac{1}{2}\left[\frac{\sin (m+n) x}{m+n}+\frac{\sin (m-n) x}{m-n}\right]+c \end{aligned}

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