Gradient

$$\nabla f=\text{grad}f=<f_x,f_y,f_z>$$

• $\nabla f$ points in the direction of greatest slope
• $|\nabla f|$ is the maximum slope of f
• $\nabla f(\vec{a})$ is a normal vector of the tangent plane of the level surface at $\vec{a}$
• Uses Del operator