# Integration Using Trigonometric Identities

#### notes

When the integrand involves some trigonometric functions, we use some known identities to find the integral as  following example.
i) int cos x^2 dx
⇒  cos 2x = 2 cos^2 x – 1, which gives
cos^2x = (1+cos 2x )/2
Therefore ,
int cos^2x dx = 1/2 int (1+ cos 2x)dx =1/2 int dx + 1/2 int cos 2x dx
=x/2 +1/4 sin 2x + C

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Integrals part 17 (Integration by trigonometric identities) [00:11:55]
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