∫xcos(x^2)dx=∫cos(x^2)(xdx)=∫cos(x^2)(d(x^2)/2)=(1/2)∫cos(x^2)d(x^2)=(1/2)sin(x^2)+C
∫xcos(x^2)dx=1/2∫cos(x^2)dx^2=1/2sinx^2+C
∫xcos(x^2)dx=1/2∫cos(x^2)dx^2=1/2sin(x^2)+C
