已知f(x)的导函数是根号下(-X^2+2X)求原函数
3个回答

∵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.