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Angle of depression

The angle of depression is the angle made by the line of sight with the horizontal when an object is seen below eye level.

Practice This Concept

Main explanation

Teacher explanation

When you stand at a window, on a terrace, or on a bridge and look down at an object, your line of sight goes downward from the horizontal. The downward angle between the horizontal line at your eye and the slant line to the object is called the angle of depression. In diagrams, it is often equal to the angle of elevation from the lower point because of alternate interior angle reasoning on parallel horizontals.

Example

A person standing on a cliff looks down at a boat in the sea. The angle between the horizontal through the person's eye and the line of sight to the boat is the angle of depression.

Simple analogy

Depression means going down, so the line of sight goes below the horizontal.

Common confusion

Students often measure the angle from the vertical drop line or from the ground, which gives the wrong angle.

Exam tip

First draw the horizontal at the observer's eye level. For depression, the line of sight goes downward below that line.

Study the angle of depression diagram carefully

Use the labelled diagram to keep angle of depression clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of angle of depression in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on angle of depression.

Revision cue

Revise angle of depression through the labels before writing the answer.

Answer writing and exam use

1-mark use

Write the exact meaning of angle of depression in one clean line.

2-mark use

Define angle of depression and add one example or condition.

3-mark use

Explain angle of depression, show the method or example, and mention the common mistake.

MCQ Quiz

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