You may find it easier to substitute something like y=sin(x) to make is a bit easier to look at. Then when you have your two values for y, you can make those equal to sin(x).
But if I post it once, will it not help him (or her) the next time - so he (or she) doesn't have to post again for a similar question?
On top of that, I'm new to using LaTeX, so I like to practise using it whenever I can
No, it encourages people to put up their homework and get it done for them and they learn little if anything. Guide them to the answer wherever possible