Author 
Message 
HashBrowns Poster
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(2ax)) 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. 
Simon Taylor Veteran poster
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? 
