Say whether each angle is an angle of elevation or an angle of depression…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Say whether each angle is an angle of elevation or an angle of depression.
- Ravi stands on the ground and looks at the top of a flagpole.
- A sailor on the top of a lighthouse looks at a ship far below.
- The ship's captain looks back at the lamp of the lighthouse.
- Compare the angles in (b) and (c) for the same line of sight.
Need a reminder? The key ideaShow
The line of sight joins the eye to the object. The angle of elevation (looking up) and the angle of depression (looking down) are measured from the horizontal. For one line of sight they are equal, because they are alternate angles between parallel horizontals.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Ravi looks up, so it is an angle of elevation.
Step 2. (b) The sailor looks down, so it is an angle of depression.
Step 3. (c) The captain looks up at the lamp, so it is an angle of elevation.
Step 4. (d) The two horizontals are parallel, so the angles are alternate angles. They are equal.
Answer: (a) elevation; (b) depression; (c) elevation; (d) equal.
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