Hi jasonk,

In your right triangle you will need to find the total distance traveled in feet. This would be the hypotenuse (c).

When you finish converting mph to ft/min, you will find that 9mph = 792 ft/min.

Divide the total distance (c) in feet by 792 feet per minute and you'll have the time in minutes that it takes to descend 80 feet at an angle of depression of 5 degrees.