The angle of elevation is measured up from the horizontal; the angle of depression is measured down from the horizontal. Draw the right-angled triangle, mark the horizontal and put the angle in the right place.
Bearings are angles measured clockwise from north, written with three digits, like 061°. To find how far east or north a ship has travelled, draw a right-angled triangle using the north line and use sin or cos. The back bearing differs by 180°.
Worked example
From 70 m away, the angle of elevation of the top of a tower is 32°. Find the height of the tower to 1 d.p.
- Height is opposite and 70 m is adjacent, so use tan.
- 70 × tan 32° = 43.74…
Answer:43.7 m
Key words
- angle of elevation
- measured upwards from horizontal
- angle of depression
- measured downwards from horizontal
- bearing
- a three-figure angle clockwise from north
Practise this
New questions every time.
Common Core-referenced: HSG-SRT.C.8