A surveyor wishes to measure the width of a trench. He places a transit telescope in a posi- tion on one side of the trench that is 18 feet higher than the second location. The surveyor
reads the angle of depression from the transit telescope and finds that it is 31°, as shown
in the diagram below.
If the transit telescope is 4.5 feet above the ground at the first location during this reading
how wide is the trench?