Not sure what I'm supposed to do, "to find an expression for sin(3x) in terms of sin"

Part of question (from assignment): Use double-angle and addition formulæ and other relations for trigonometrical functions to find an expression for sin(3x) in terms of sin x alone.

I don't know what is meant by "to find an expression for sin(3x) in terms of sin x alone". I've found a working through of a very similar question but still don't get what is meant by it. I know how to "Use double-angle and addition formulæ and other relations for trigonometrical functions" but I don't get what I'm supposed to be doing with them.

This may seem stupid but I couldn't find an answer on google :/

Would really appreciate some help with this!

PS. This is actually for a university calculus paper but this seems like it would fit better here (sorry if it doesn't!).