The integral is given below as,
I= ∫ xsin3x dx
Use integration by parts rule. Consider x as first function and sin3xas second function.
I=x ∫ sin3xdx− ∫ ( d dx x ∫ sin3xdx )dx =x( − cos3x 3 )− ∫ ( − cos3x 3 ) dx =− xcos3x 3 + 1 3 ( sin3x 3 )+C I=− xcos3x 3 + 1 9 sin3x+C
Thus, the integration of ∫ xsin3x dx is − xcos3x 3 + 1 9 sin3x+C.