Final answer:
Using trigonometry and the cosine function, a 24-foot ladder leaning at an 80° angle with the ground reaches approximately 4.2 feet up the wall.
Step-by-step explanation:
To determine how high up the wall a 24-foot ladder reaches when it is leaning against the wall at an 80° angle with the ground, we can use trigonometry. Specifically, we will use the cosine function, which relates the adjacent side of a right triangle (the height the ladder reaches up the wall) to the hypotenuse (the length of the ladder).
The cosine of an angle in a right triangle is equal to the length of the adjacent side divided by the length of the hypotenuse. So we can set up the equation as follows:
To find the height, we rearrange the equation:
Then we use a calculator to find the cosine of 80 degrees and multiply by 24:
height ≈ 24 × 0.1736 ≈ 4.1664 feet
Rounding to the nearest tenth of a foot gives us: height ≈ 4.2 feet
Therefore, the ladder reaches approximately 4.2 feet up the wall.