∫xcos(4x^2 +5)dx
let 4x^2+5=t
dt=d(4x^2+5)=4d(x^2)=4*2xdx=8xdx so dx=[dt/8x]
∫xcos(4x^2 +5)dx=∫xcostdt/8x=1/8∫costdt=1/8sint
=1/8(4x^2+5)
写了这么久,竟然没有悬赏分?...