In order to make the technology fit the idea, x and y are denoted as X and Y. u' is also the partial derivative of the function f with respect to X and v' is the partial derivative of f with respect to Y.[br][br]Go ahead and slide the values of X and Y. The trace function is on so as to demonstrate the shapes as the function f has varying input.[br][br]Why is a parabola formed when you move the slider around for Y? Why is it a line?