Not sure if this is the correct place to post this. dy/dt = 0, find y(t) My professor told me that the chain rule is used to determine that (dy/dt)*dt = dy, but I just don't see it. Multiply both sides by dt. (dy/dt)*dt = 0dt (dy/dt)*dt = 0 dy = 0, then integrating both sides: y = C dy/dt is the derivative of the function y in respect to t, and dt is just a small change in t. How is the chain rule used here? dz/dx = dz/dy * dy/dx makes a lot more sense to me, but I just don't see that here.