3D Evaluate

The evaluate function can return a z-value for a given set of x and y values. Or, for polar equation, a z-value for a given set of r and t values. To access this function, right click on the 3D graph and choose Evaluate.

In the evaluate dialog box, enter an x value, a y value (r and t for polar) and which equation you'd like to evaluate, and a z value will be returned.