integral cos (x^3) dx is?
1 Answer
embizze | High School Teacher | (Level 2) Educator Emeritus
Evaluate `int cos^3x dx` :
Rewrite as `intcos^3xdx=int(cos^2x)cosxdx`
`=int(1-sin^2x)cosxdx`
Let `u=sinx,du=cosxdx` Then
`int(1-sin^2x)cosxdx=int(1-u^2)du`
`=intdu-intu^2du`
`=u-1/3u^3+C_1` Substituting for `u` we get:
`=sinx-1/3sin^3x+C`
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`intcos^3xdx=sinx-1/3sin^3x+C`
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