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Find the integrals of the function: sin 4x sin 8x - Mathematics

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Question

Find the integrals of the function:

sin 4x sin 8x

Sum
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Solution

Let `I = int sin 4x sin 8x`

`= 1/2 int 2 sin  4x sin 8x  dx`

`= 1/2 int (cos 4x - cos 12 x) dx`     ....[∵ 2 sin A sin B =  cos (A - B) - cos (A + B)]

`= 1/2 [1/4  sin 4x - 1/12  sin 12 x] + C`

`= 1/8 [sin 4x - 1/3  sin 12 x] + C`

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Chapter 7: Integrals - Exercise 7.3 [Page 307]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 7 Integrals
Exercise 7.3 | Q 7 | Page 307

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