Volume 3: The Calculus of Life

Workbook 26.2: The Fundamental Theorem

Directives for the Bridge-Crosser:

1. Integrate: Find the anti-derivative ($F$). Leave off the $+C$.
2. Upper Bound: Plug the top number ($b$) into $F(x)$.
3. Lower Bound: Plug the bottom number ($a$) into $F(x)$.
4. Subtract: Result $= F(b) - F(a)$.

Part I: Basic Area Evaluations

Use the FTC to find the exact area for each function.

$\int_{0}^{3} x^2 dx$

$F(x) = x^3 / 3$
$F(3) = 3^3 / 3 = 9$
$F(0) = 0^3 / 3 = 0$
Area = $9 - 0 = \mathbf{9}$.

$\int_{1}^{4} (2x + 5) dx$

...

$\int_{0}^{\pi} \sin x dx$

$F(x) = -\cos x$
$F(\pi) = -\cos(\pi) = -(-1) = 1$
$F(0) = -\cos(0) = -1$
Area = $1 - (-1) = \mathbf{2}$.
The Logic Check:

Why is the area under a Sine wave from 0 to $\pi$ exactly 2? Try to visualize the wave. Does it seem strange that a "Curved" wave gives such a clean "Whole" number for its area? What does this tell you about the design of the circle?

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Part II: Transcendental Area

$\int_{0}^{2} e^x dx$

...

$\int_{1}^{e} \frac{1}{x} dx$

$F(x) = \ln|x|$
$F(e) = \ln(e) = 1$
$F(1) = \ln(1) = 0$
Area = ...

Part III: Average Value of a Season

Use the formula $\text{Avg} = \frac{1}{b-a} \int_{a}^{b} f(x) dx$.

Find the average value of $f(x) = x^2$ on the interval $[0, 3]$.

Step 1: Integral = 9 (from Problem 1).
Step 2: $b-a = 3-0 = 3$.
Average = $9 / 3 = \mathbf{3}$.

Part IV: The Challenge (The Net Change)

The Displacement of the Heart

A person's "Growth Rate" is given by $v(t) = 3t^2 - 12t$.
1. Calculate $\int_{0}^{4} v(t) dt$.
2. Notice your answer is zero.
3. Does this mean they didn't do anything? Or does it mean they returned to the same spot?

...

Part V: Transmission (The Echad Extension)

Teacher Log: The Ruler Secret

Objective: Explain the FTC to a younger student using a ruler.

The Activity:
1. Lay a ruler on the table.
2. Place a toy at 2 inches.
3. Move the toy to 8 inches.
4. "I didn't count every tiny sliver of distance. I just subtracted 2 from 8."

The Lesson: "Math can find the 'Total' by just looking at the 'Before' and 'After'."


Response: ___________________________________________________________

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