This widget is honestly insane. It will compute up to 340 partial derivatives. The first column of outputs represents partial x, the second column represents partial y, the third column represents partial z, and the fourth column represents partial w.
If you a trying to compute the gradient vector for a function tell the widget to compute all first order partial derivatives.
This will produce and graph a tangent plane to a function at a point.
This will produce the normal line to a curve.
This widget will compute the directional derivative in the direction of the unit vector given by [cos(theta), sin(theta)].