Hello. To perform better in mathematics, here are the few tips

1. Practice daily. Whichever sum you take, practice till the end till you reach the result, whether result might be right or wrong, solve till the end

2. After you get perfection with solving the sums and getting right answer, solve sums with in time limit. Have a time limit and solve the problem

3. Spare an hour or two minimum per day. Make it as a part of day

In trigonometry especially, first have a note of all the formulae, they are very important.

Solve as many sums as you can, it gets improved eventually

Here is a good reference book for practice

Trigonometry Advanced Placement Version Sixth Edition, 2001st Edition I.M. Gelfand, Mark Saul