## Elementary Geometry for College Students (6th Edition)

$s \times sin36^{\circ}$
We know that each angle of a pentagon is 108 degrees. Thus, the bisected angle is 54 degrees, making the other angle 36 degrees. Thus, we solve for the altitude: $sin36^{\circ} = \frac{h}{s} \\ h = s \times sin36^{\circ}$