Sigma notation, trig and functions are generally covered in pre-calculus, but I think to be on the safe side you will want to look at Calculus too at least for infinite series.
Books I would recommend
It would be best to cover pre calculus first, maths can be intimidating at times but honestly the more you learn the less you will feel discouraged, the best way to understand maths imo is through applications, its all well and truly nice being able to evaluate formulas but it all only truly makes sense when you see it applied to real life scenarios, Calculus books tend to be better at this as real life scenarios are usually changing
WOW! How can the authors of "Stewarts Pre-Calculus" justify price of 260$ for a book with 397 pages. Now thats a rip off if i ever seen one. Thanks for this advice, i gotta save for few months to get it....
EDIT: AH! Thank god for internet, got both books for "free".