# Studying for my Trig Final but having some probs

• Apr 27th 2009, 11:18 AM
jasonk
Studying for my Trig Final but having some probs
1. Angle of Depression
A submarine traveling 9.0mph is descending at an angle of depression of 5°. How many minutes does it take the submarine to reach a depth of 80 ft.
I have
9mph x 5280ft/1mi x 1hr/60 min
and then I know I am supposed to draw a triangle with angles 5° and 85° but I am stuck after that.
• Apr 27th 2009, 12:52 PM
masters
Quote:

Originally Posted by jasonk
1. Angle of Depression
A submarine traveling 9.0mph is descending at an angle of depression of 5°. How many minutes does it take the submarine to reach a depth of 80 ft.
I have
9mph x 5280ft/1mi x 1hr/60 min
and then I know I am supposed to draw a triangle with angles 5° and 85° but I am stuck after that.

Hi jasonk,

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

$\displaystyle \sin 5^{\circ}=\frac{80}{c}$
$\displaystyle c=\frac{80}{\sin 5}$

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.