Trig question - should be easy but it's probably lacking information A person I know had this question on his 9th grade school test: > You are standing on the edge of a cliff. Looking down from the cliff you see a river that is $3$ miles from the base of the cliff. Directly above the river you can see an airplane that is flying $7$ miles above the river. From your perspective of the cliff, what is the angle of elevation and what is the angle of depression? As far as I can say, there is insufficient data: we know that the altitude of the plane is $7$ miles (the "base" of the triangle) and the "height" of the triangle is $3$. If we sketch it, we basically have two right triangles. but we do not know what is the height of the cliff. That to me seems like a key piece of information. Am I correct? This would make the question not suitable for a test.

_I should probably have written my comment as an answer. For the sake of completeness, since this problem is solved, I will write it here._

Yes, you are correct. Any height of the cliff is possible, thus any possible angle.