Skip to main content\(\newcommand{\deriv}[2]{\displaystyle \frac{d#1}{d#2}}
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Instructions.
Drag the blue unit vector
\(\mathbf u\) around the circle of directions and watch the meter display
\(D_{\mathbf u} f = |\nabla f|\cos\theta\text{.}\) Use the buttons to snap
\(\mathbf u\) to the three special cases: the same direction as
\(\nabla f\) (fastest increase), the opposite direction (fastest decrease), and a direction orthogonal to
\(\nabla f\) (no change).