Directional Derivatives
This applet illustrates the concept of directional derivative.
- Set the coordinates of point with the X and Y sliders.
- Set the direction of the unit vector with the Angle slider. (So the components of are the cosine and sine of the chosen Angle.)
- Observe the curve that results from the intersection of the surface of the function with the vertical plane containing .
- The directional derivative of the function at the point along the direction of the vector is the slope of the tangent line to the previously described curve at .