The text translated: From a point A on a water we observe a antenna on a mountain. The antenna is 23m high. Find the height of the mountain.
I believe the solution is in the differences between the angles. But please, only subtle hints. This is homework and I like the creative process of pondering on it myself. Right now I'm stuck. I know that sine, cos and tan is only defined for right angled triangles.
Hints people, do not just dump the answer.