How fast is it moving?

You will find how far an object at a fixed height has moved between two sightings, and how fast it moves.

Your tasks.

1. In distance_moved, return the distance moved when the angles of elevation are first and then second, at a fixed height h. The object moves away, so second is the smaller angle.
2. In speed, return the distance moved divided by seconds.
3. In time_left, return the time a boat still needs to reach the foot of a cliff of height h after the second sighting. It moves at the speed you found, and the angles are angles of depression.
4. Set plane to the speed of an aeroplane at $500$ m that is seen at $60°$ and then at $30°$, $8$ seconds apart.