Question

a 25 - foot long ladder is propped against a wall at an angle of 18° with the wall. how high up the wall does the ladder reach? round the answer to the nearest tenth of a foot.
13.8 ft
23.8 ft
26.3 ft
80.9 ft

Explanation:

Step1: Use cosine function

Let the height on the wall be $h$. We know $\cos\theta=\frac{h}{l}$, where $\theta = 18^{\circ}$ and $l = 25$ ft. So $h = l\cos\theta$.

Step2: Calculate the value

$h=25\times\cos(18^{\circ})\approx25\times0.9511 = 23.8$ ft

Answer:

23.8 ft