## Precalculus (6th Edition) Blitzer

Let us suppose $\theta$ to be the angle of elevation, h to be the height of the arch and $r$ to be the radius. Apply the tangent ratio to get \begin{align} & \tan \theta =\frac{h}{r} \\ & h=r\tan \theta \end{align} Thus, the above statement provided is sufficient to find the height of the arch.