angle of depression

Definition of Angle of Depression


The word “depression” means “fall” or “drop”.

Angle of depression is the angle between the horizontal and the line of sight to an object beneath the horizontal.

Take a look at the example below.

Example - Angle of Depression


In the picture below, an observer is standing at the top of a building and looking straight ahead at the birds (horizontal line). The observer must lower his eyes to see the car parked (slanting line).


The angle formed between the two lines is called the angle of depression.

Solved Example on Angle of Depression


An airplane is flying at a height of 2 miles above the level ground. The angle of depression from the plane to the foot of a tree is 15°. Find the distance that the air plane must fly to be directly above the tree.



Step 1: Let’s first visualize the situation.

Step 2: Let ‘x’ be the distance the airplane must fly to be directly above the tree.


Step 3: The level ground and the horizontal are parallel, so the alternate interior angles are equal in measure.




Step 6: So, the airplane must fly about 7.46 miles to be directly above the tree.

Related Terms for Angle of Depression
  • Angle
  • Horizontal Line