Integrate:-\\xcos3xdx

Dear Aparna,

 cos(3x) = 4 cos³(x) - 3 cos(x)

substitute value of cos³(x) from above in the integral and solve by parts.

Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

Win exciting gifts by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian.

Now you score 5+15 POINTS by uploading your Pic and Downloading the Askiitians Toolbar  respectively : Click here to download the toolbar..

Askiitians Expert

Anil Pannikar

IIT Bombay

I = xcos³xdx

 integrating it by parts

 =x[cos³xdx] - {[cos³xdx]}dx

 now put cos³x = (cos3x+3cosx)/4   and integrate