### Why do this
problem?

There are several different ways of solving

this
problem. It is a good example to bring home the point that, to
be an expert problem solver, and to understand a piece of
mathematics, it is not enough to find an answer. One should ask
oneself "Have I used the best method?". This problem can be solved
using trig formulae and the cosine rule but it can be solved more
straightforwardly using only Pythagoras theorem.

### Possible approach

Challenge the class to find different methods of solution.

### Key question

How do we interpret the two solutions?

Is the diagram correct for both solutions?