Graphical Derivatives: Tangent Slope Visualizer

The most common confusion students have when trying to visualize or understand derivatives on a graph itself is the distinction between the actual function f(x) and the derivative function f'(x) itself. This interactive visualization is designed to help.

For any given x value, you can drag the green number to one of the two equations above:

Drag to the f(x) equation (on the left)

• You'll find the height (or y-value) of the white graph at that x-value.

Drag to the f'(x) equation (on the right)

• You'll find the slope at that x-value. You'll see a tangent line drawn on the graph when you drag it to the correct equation.

Formula

f(x)=height of the graphf(x)=slope of the graph at x\begin{gathered} f({\color{#34d399}x}) = \text{height of the graph} \\ {\color{#c084fc}f'({\color{#34d399}x})} = \text{slope of the graph at } {\color{#34d399}x} \end{gathered}

Easy Example Problem

If a function is given by f(x) = x³ - 3x, identify the x-intercepts and signs of its derivative f'(x) graphically.

1. Find the horizontal tangents: f'(x) = 3x² - 3 = 0 ⟹ x = ±1. These points map to intercepts on the f'(x) graph.

2. For x < -1, the slope is positive since the function increases.

3. For -1 < x < 1, the slope is negative since the function decreases.

4. For x > 1, the slope is positive. Thus, f'(x) is a parabola that is positive, dips below the x-axis between -1 and 1, and rises above it again.

Interactive Preview

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