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Tamil Nadu Board of Secondary EducationHSC Science Class 11

Integrate the following functions with respect to x : sin4xsinx - Mathematics

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Question

Integrate the following functions with respect to x :

`(sin4x)/sinx`

Sum

Solution

`int (sin4x)/sinx  "d"x = int  (sin2(2x))/sinx * "d"x`

[sin 2A = 2 sin A cos A]

= `int (2sin 2x cos 2x)/sinx  "d"x`

= `2 int (2sinx cosx * cos 2x)/sinx * "d"x`

= `4int cos 2x cos x * d"x`

= `2 int 2 cos 2x cosx * "d"x`

= `2 int [cos(2x + x) + cos(2x - x)]  "d"x`

[2 cos A cos B = cos(A + B) + cos(A – B)]

= `2 int (cos 3x + cosx)  "d"x`

= `2 int cos 3x  "d"x + 2int cos x  "d"x`

= `2 (sin3x)/3 + 2 sin x + "c"`

= `2 [(sin 3x)/3 + sin x] + "c"`

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Chapter 11: Integral Calculus - Exercise 11.5 [Page 202]

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Samacheer Kalvi Mathematics - Volume 1 and 2 [English] Class 11 TN Board
Chapter 11 Integral Calculus
Exercise 11.5 | Q 9 | Page 202
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