根號(hào)下（2x-x^2） =根號(hào)下（1-(x-1)^2)
x-1=sint,x=1+sint,t=arcsin(x-1),dx=cost dt
原積分=Scost *cost dt
=S(cos2t+1)/2 *dt
=1/2*Scos2tdt+1/2*Sdt
=1/4*sin2t+1/2*t+c
=1/2*(x-1)*根號(hào)下（2x-x^2）+1/2*arcsin(x-1)+c
1/根號(hào)下（2x-x^2）=1/根號(hào)下（1-(x-1)^2）
x-1=sint,x=1+sint,t=arcsin(x-1),dx=cost dt
原積分= S1/cost *costdt
=Sdt
=t+c
=arcsin(x-1)+c