Angles of Elevation & Depression Flashcards

All 4 cards in this deck

What is an angle of elevation?

The angle measured upwards from the horizontal to the line of sight of an object above.

What is an angle of depression?

The angle measured downwards from the horizontal to the line of sight of an object below.

True or false? The angle of elevation of B from A is equal to the angle of depression of A from B.

True. The two horizontal lines are parallel, so the angles are alternate angles.

What are the steps to find a height from an angle of elevation?

e.g. angle of elevation $30^\circ$ from a point $20$ m from the base of a tower

1. Sketch the right-angled triangle: $20$ m adjacent, height $h$ opposite the $30^\circ$
2. Choose the ratio: $\tan 30^\circ = \frac{h}{20}$
3. Work it out: $h = 20 \times \tan 30^\circ = 11.5$ m (1 d.p.)