Why does my child put the angle of depression in the wrong place?
Your child measures an angle of elevation or depression from the vertical instead of the horizontal.
Why children do it
Looking down from a cliff, the angle seems to belong at the top of the triangle, against the cliff. But an angle of depression is measured down from the horizontal, level with the eye, not from the cliff. It equals the angle of elevation looking back up from the bottom, which is the one to use.
How to help at home
Ask them to draw the horizontal line first: elevation and depression are measured from it.
The right way
From 20 m away, the angle of elevation to the top of a tree is 35°. How tall is the tree, to 1 decimal place?
- 14.0The height is opposite and 20 m adjacent: 20 × tan 35° = 14.00..., so 14.0 m.
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