Solve by using integration by parts twice

[Angela Chan]

Please see the attached file

 

[skeeter]

may be easier using a product to sum identity ...

 

[Deleted member 4993]

Please see the attached file

Use:
2 * sin(A) * sin(B) = cos(A-B) - cos(A+B).............................. as advised in response #2 ↑

 

[skeeter]

if you insist on using parts, recommend letting [MATH]u = \sin(3x) \text{ and } dv = \sin(2x) \, dx[/MATH] for the initial iteration