Calculate Crane Height from Angle Measurement

[Cbray]

To calculate the height of a crane which is on top of a building, dennis measures the angle of elevation to the bottom and the top of the crane. these were 62 degrees and 68 degrees respectively. if the building is 42 metres high find the height of the crane.

I'm asking for a friend, excuse the English it was sent through an instant message.
He would prefer the answer (and working if possible), thanks! :)

 

[Mentallic]

We can't just give out answers, it's a rule. We need to see what he's tried first.

You (or your friend) should begin by finding out how far the person is from the building. Use the fact that the bottom of the crane is equal to the top of the building which is 42m high.