Quick question. This is kind of embarrassing actually. Suppose I have functions x(t,s) and y(t,s) (say they're parametric equations of a surface of something) and I want to know what dy/dx is. Specifically, I have x and y in terms of the parameters, which are kind of complicated functions, and I want to know what that derivative is in terms of dx/dt, dx/ds, etc. I know if they were functions of just 1 parameter, then it would just be dy/dx = (dy/dt)/(dx/dt), but with 2 I'm confused. Can you guys help me out?!?