Answer
$ \theta \approx 15.9^{\circ}$
Work Step by Step
The trigonometric functions can be expressed as:
$\sin \theta=\dfrac{Opposite}{Hypotenuse} \\ \cos \theta=\dfrac{Adjacent}{Hypotenuse} \\ \tan \theta=\dfrac{Opposite}{Adjacent}$
We are given the opposite side and adjacent side. Our aim is to compute the the angle. So we use Tangent.
Let $a$ be the height of the ladder that touches the building and consider it as the opposite side.
Since, $\tan \theta=\dfrac{Opposite}{Adjacent}$
Therefore, $\tan \theta=\dfrac{10}{35} \implies \theta =\arctan (\dfrac{10}{35})$
or, $\theta \approx 15.9^{\circ}$
