Question

A

The top of a signal tower is 135 meters above sea level. The angle of depression from the top of
the tower to a passing ship is 20°. How many meters from the foot of the tower is the ship? Round
to the nearest meter.

Answer 1

371 meters

Explanation:

This is a triangle trigonometry problem. The phase "angle of depression" means the angle looking down to the boat instead of looking straight out from the top of the tower. See image. You can then find the rest of the angle is 70°. Looking at the boat creates one line, the tower is another side, 135m, and the distance to the boat is the third side of a triangle. See image.

Tangent is a trig ratio. It compares the side opposite from the angle to the side next to (adjacent) the angle. We can then write an equation. Unless the teacher/program/text gives you tan 70°, you need a calculator to find it.

tan 70° = x/135

Multiply both sides by 135.

135 tan 70° = x

Put this in a calculator.

135 × tan70°

it comes out a long decimal. But the directions said to round to the nearest meter.

The boat is about 371 meters away from the foot of the tower.