Depends.
December: I highly recommend you just relax. Like, seriously. You won't get a holiday like that for a whole year. And the year is going to feel VERY long. RIDICULOUSLY long.
Then when semester starts, I probably would just look at the different kinds of functions. I wouldn't worry about circular functions just yet though.
by book:
Essentials: Chapters 1, 3, 4, 5.
Maths Quest: Chapters 1, 2, 3, 4, 5. Do note: If you are using Maths quest, there is a high chance that you will also be learning binomial theorem in the first few weeks of school. Completely useless information, but it might be on a sac
Heinemann: Chapters 1 & 2
That will pretty much cover what you will learn in term 1, which means once school starts again (plus all the usual interruptions in term 1), you will be able to ask your teachers more specific detail on things you aren't sure about.
BUT: This is the MORE important bit.
If there is ANYTHING in the year 11 course, ANYTHING at all, revise THAT first. You will probably not get a chance to fix it!