Question

A ladder 20 m long touches a wall at the height of 10 m. Find the angle made by the ladder with the horizontal.

Answer 1

Let $AC$ be the ladder such that $AC=20$ m. It touches the wall at a height $AB\hspace{0.17em}=10$ m.
Let $\theta$ be the angle.

In ∆$ABC$, we have:
$\sin \theta =\frac{AB}{AC}=\frac{10}{20}=\frac{1}{2}$

⇒ $\theta ={30}^o$

Hence, the angle made by the ladder with the horizontal is 30°.