Anti-derivative of a trig equation

  • Thread starter Thread starter togame
  • Start date Start date
  • Tags Tags
    Trig
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 2K views
togame
Messages
18
Reaction score
0

Homework Statement


I just need to find the anti-derivative of this equation:
[itex]\int x(sin^2(3x)cos(3x))dx[/itex]



Homework Equations


[itex]sin^2(x)+cos^2(x)=1[/itex]


The Attempt at a Solution


I'm not really sure where to start here. I tried to do a substitution first but couldn't make it work. So then I tried to put sin^2 in terms of cos^2 but that didn't seem to help me out any more. Anyone have an idea of how to tackle this problem? Thanks in advance!
 
Physics news on Phys.org
togame said:

Homework Statement


I just need to find the anti-derivative of this equation:
[itex]\int x(sin^2(3x)cos(3x))dx[/itex]



Homework Equations


[itex]sin^2(x)+cos^2(x)=1[/itex]


The Attempt at a Solution


I'm not really sure where to start here. I tried to do a substitution first but couldn't make it work. So then I tried to put sin^2 in terms of cos^2 but that didn't seem to help me out any more. Anyone have an idea of how to tackle this problem? Thanks in advance!

Integrate by parts, with u = x, dv = [itex]\sin^2(3x)\cos(3x)dx[/itex].

To integrate [itex]\sin^2(3x)\cos(3x)dx[/itex], use the substitution [itex]y = \sin(3x)[/itex]
 
Curious3141 said:
Integrate by parts, with u = x, dv = [itex]\sin^2(3x)\cos(3x)dx[/itex].

To integrate [itex]\sin^2(3x)\cos(3x)dx[/itex], use the substitution [itex]y = \sin(3x)[/itex]

Thank you very much. I didn't see the ability to do another substitution right off hand.