This problem involves a right-angled triangle where:

• The hypotenuse (ladder) = 5 m
• The adjacent side (distance from wall) = 1.0 m
• The angle θ is the one between the ladder and the ground.

We use the cosine function:

$\cos(\theta) = \frac{\text{adjacent}}{\text{hypotenuse}}$

$\cos(\theta) = \frac{1.0}{5.0}$

$\theta = \cos^{-1}(0.2)$

Using a calculator:

$\theta \approx 78.5^\circ$

Correct Answer:

b. 78.5°

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Here are 5 related questions:

1. If the base of the ladder were 2 meters away, what would the new angle be?
2. How high does the ladder reach on the wall?
3. What is the sine of the angle the ladder makes with the ground?
4. If the ladder were 6 meters long, how would the angle change?
5. What is the minimum distance the ladder’s base should be to avoid slipping?

Tip: Always use inverse trigonometric functions (like $\cos^{-1}, \sin^{-1}$) when solving for angles in right triangles.