∫arctan√x dx令√x=t,x=t^2,dx=dt^2所以原式=∫arctantdt^2=t^2*arctant-∫t^2/(1+t^2)dt=t^2*arctant-∫(t^2+1-1)/(1+t^2)dt=t^2*arctant-t+arctant+c=xarctan√x-√x+arctan√x+c