Hi, i have a question on taking derivative w.r.t. to a function (instead of an independent variable). Actually i saw an excellent post on this same forum but that one was about a single variable. My question is: f is function of x and y, and z is some other function also dependent on x and y, so is the following correct? df/dz=df/dx*dx/dz+df/dy*dy/dz it differs from the classic chain rule in the sense that z is actually a function (not an independent var), so i am not sure about this. I appreciate so much for any comment!