z=x^2+y^2,而x=1+sint,y=cost,求dz/dt.

z=x^2+y^2,而x=1+sint,y=cost,求dz/dt.

用分部求導法
dx/dt = cost
dy/dt = -sint
而dz/dt=(dz/dx)*(dx/dt)+(dz/dy)*(dy/dt)
=2x(cost)-2y(sint)
=2(1+sint)cost-2costsint
=2