You do not need to have met hyperbolic trig functions before in
order to do this question as the definitions are given and you are
led through the question step by step. You could look up the
results and the proofs of the hyperbolic trig identities but you
will gain much more from thinking through these proofs for
yourself.
Possible extension:
Prove, by induction or otherwise, that for $x> 0$ and positive
integral values of $n> 1$ $$\sinh nx > n\sinh x.$$