Post Number: 9
|Posted on Saturday, 16 June, 2012 - 05:47 pm: |
I am stuck on this problem.
Prove that for values of 2a to 0 for x, Integral (f(x)) dx = Integral for values of a to 0 for x, of (f(x) + f(2a-x)) dx.
Hence, find Integral from pi to 0, of xsin(x)sin(3x) dx
I found xsin(x)sin(3x)= xsin^2(2x) - xsin^2(x), but am confused on how to reach the suggested value of the integral = 0.
I would be grateful for any help.
Post Number: 670
|Posted on Monday, 18 June, 2012 - 03:46 pm: |
Before trying any trig identities, how about applying the rule you just found to the integral?