1.9. Example 1.27: Height Calculation of a Lighthouse

Try these first

1. 1.

   What is an angle of depression?

   Hint

   Think about how you would describe looking down at something.

2. 2.

   What does cotangent of an angle represent?

   Hint

   Recall how tangent is the opposite over adjacent.

3. 3.

   What is the height of a lighthouse if the angles of depression to two ships are 30° and 45°?

   • 40 m
   • 50 m
   • 60 m

   Hint

   Calculate using Height = 100 / (cot(30°) - cot(45°)).

4. 4.

   True or False: The angle of depression is always measured upward from horizontal.

   • True
   • False

   Hint

   Think about how you observe objects below.

5. 5.

   From the top of a tower, the angles of depression to two points on the ground are 20° and 50°; if they are 150 m apart, find the height of the tower.

   Hint

   Break down the angles and distances before calculating the difference.