∵f′(x)=√(-x^2+2x)=√[1-(x-1)^2],∴f(x)=∫√[1-(x-1)^2]dx.
令x-1=sinu,得:u=arcsin(x-1),dx=cosudu.
∴f(x)
=∫√[1-(sinu)^2]cosudu=∫(cosu)^2du=(1/2)∫(1+cos2u)du
=(1/2)∫du+(1/4)∫cos2ud(2u)=(1/2)u+(1/4)sin2u+C
=(1/2)arcsin(x-1)+(1/2)sinucosu+C
=(1/2)arcsin(x-1)+(1/2)(x-1)√[1-(sinu)^2]+C
=(1/2)arcsin(x-1)+(1/2)(x-1)√[1-(x-1)^2]+C
=(1/2)arcsin(x-1)+(1/2)(x-1)√(2x-x^2)+C.