Question

cos3x integral

Answer 1

\[\int\cos(3x)\,\mathrm dx\]

Answer 2

let 3x = u
3dx = du
dx = du/3

\[\int\cos(u)\,\frac{\mathrm du}3\\=\frac13\int\cos(u)\,\mathrm du\]

Answer 3

\[\int\limits\limits \cos(3x)dx\] use chain rule, whats the integral of cosine? use u-substitution

Answer 4

darnit Rhaukus :P

Answer 5

beat ya to it q:

Answer 6

can you integrate cosine @jahan?

Answer 7

Carrying on from @UnkleRhaukus You get, \[\frac{ 1 }{ 3 }\int\limits cos(u)du\] \[\frac{ 1 }{ 3 }\sin(u) +c\] input 3x back in for u\[\int\limits \cos(3x)dx=\frac{ \sin(3x) }{ 3 }+c\]

Answer 8

He'll probably come back to tell you guys it's really cos^3x :P

Answer 9

<_________<

Answer 10

If it is, then break it up into \[\large (\cos x)(\cos^2x) = \cos x(1 - \sin^2 x)\] then let u = sinx.

Answer 11

mmhmm.

Answer 12

Hello @jahan , great to see you here on OpenStudy. Hope you liked the help given by our most experienced and brilliant users that are one of your friends :)

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