Section 3.2

Interpretation of the Derivative

Beyond the formula: Understanding the derivative as slope, rate of change, and velocity.

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Deep Dive

The derivative provides three layers of meaning:

Geometric

It is the slope of the curve.

If , the graph is rising.
If , it is falling.

Rate of Change

It measures the instantaneous rate of change of with respect to .

"How fast is the function changing right now?"

Physics

If describes position, then describes velocity.

Acceleration is the derivative of velocity!

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Worked Example: Particle Motion

The position of a particle is given by meters. Find the velocity at seconds.

Step 1: Set up the Definition

We use the limit definition of the derivative:

Substitute :

Step 2: Expand and Simplify

Expand and :

Distribute and cancel terms:

Step 3: Evaluate Limit

Factor out from the numerator:

As , terms with vanish:

Step 4: Evaluate at t=4

Interpretation: The particle has momentarily stopped moving at .

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Interactive Visualization

Visualizing Motion

Explore the relationship between Position (Blue) and Velocity (Red). Notice that when Velocity is 0 (at x=0 and x=4), the Position graph has a horizontal tangent (a turning point).

Original Function f(x)
Tangent Line
Derivative Function f'(x)
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Practice Quiz

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