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An observer stands on top of a cliff and looks down at a boat below. What is the angle between the line of sight and the horizontal called?
AThe angle of depression
BThe angle of elevation
CThe angle of incidence
DThe angle of inclination
Answer & Solution
Correct answer: A. The angle of depression
1. The boat sits below the horizontal plane through the observer's eyes.
2. The angle of depression is the angle formed by the line of sight and the horizontal plane for an object below it.
3. The angle of elevation from the boat back up to the observer has the same size.
4. The angle of inclination is another name for the angle of elevation, so it names the upward case.
_Source: Siyavula Mathematics Grade 10 (Everything Maths, CC BY 4.0), Chapter 11: Trigonometry_
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