∫e^2xcos3xdx
= (1/2)∫cos3xd(e^2x)
= (1/2)[cos3x*e^2x+3∫sin3x*e^2xdx]
= (1/2)cos3x*e^2x+(3/2)∫sin3x*e^2xdx
= (1/2)cos3x*e^2x+(3/4)∫sin3x*d(e^2x)
= (1/2)cos3x*e^2x+(3/4)[sin3x*e^2x-3∫cos3x*e^2xdx]
= (1/2)cos3x*e^2x+(3/4)sin3x*e^2x-(9/4)∫cos3x*e^2xdx
= [(1/2)cos3x*e^2x+(3/4)sin3x*e^2x](4/13)
= (2/13)cos3x*e^2x+(3/13)sin3x*e^2x
= [(e^2x)/13][2cos3x+3sin3x]