Volume 2: The Logic of Creation

Workbook 20.2: The Border of Awe

Directives for the Convergence Specialist:

1. Check the Ratio ($r$): A series only has a limit if $|r| < 1$.
2. Identify $a_1$: This is your starting point.
3. The Sum Formula: $S_{\infty} = a_1 / (1 - r)$.
4. Limit at Infinity: As the bottom of a fraction gets infinitely big, the whole fraction gets infinitely small (zero).

Part I: Convergent vs. Divergent

Mark each series as either **Convergent** (has a limit) or **Divergent** (explodes to infinity).

Series A: $10 + 5 + 2.5 + 1.25...$

$r = 5/10 = 0.5$.
Since $0.5 < 1$, the series is **Convergent**.

Series B: $1 + 3 + 9 + 27...$

$r = ...$
Series is ...

Series C: $100 - 50 + 25 - 12.5...$

$r = -0.5$.
Is $|-0.5| < 1$? Yes.
Series is ...

Part II: Taming the Infinite (Infinite Sums)

Find the exact limit of these infinite geometric series.

The Bread: $1/2 + 1/4 + 1/8 + 1/16...$

$a_1 = 1/2, r = 1/2$.
$S = (1/2) / (1 - 1/2) = (1/2) / (1/2) = ...$

The Step: You take a step of 6 feet. Your next step is 2 feet. The next is 2/3 feet.
If you do this forever, how far will you travel?

$a_1 = 6, r = 1/3$.
$S = 6 / (1 - 1/3) = 6 / (2/3) = ...$
The Logic Check:

If you have an infinite series where $r = 1$, like $5 + 5 + 5 + 5...$ is it convergent or divergent? Why can't we find a "Limit" for this sum?

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Part III: Limits at Infinity

Evaluate these limits as $x$ approaches infinity ($\infty$).

$\lim_{x \to \infty} (10 / x)$

As $x$ gets huge, the fraction gets close to ...

$\lim_{x \to \infty} (\frac{2x + 5}{x})$

Hint: Divide everything by $x$.
$\lim_{x \to \infty} (2 + 5/x) = 2 + 0 = ...$

Part IV: The Challenge (The Bouncing Ball)

The Total Path

A ball is dropped from a height of 20 meters. It bounces back up to 75% of its previous height ($r=0.75$).
1. Calculate the infinite sum of all the **Upward** bounces ($a_1 = 15$).
2. Calculate the infinite sum of all the **Downward** paths ($a_1 = 20$).
3. Add them together to find the total distance the ball travels before it stops.

Sum Up: $15 / (1 - 0.75) = ...$
Sum Down: $20 / (1 - 0.75) = ...$
Total: ...

Part V: Transmission (The Echad Extension)

Teacher Log: The Half-Cake

Objective: Explain the limit to a younger student using food.

The Activity:
1. Take a cookie. Eat half.
2. Give them half of what's left.
3. Take half of what's left.
4. Ask: "If we do this all day, will we ever eat more than just this one cookie?"

The Lesson: "Infinite pieces can still fit inside one whole. That's how God fits His infinite love inside our one heart."


Response: ___________________________________________________________

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