I don't know if it is appropriate to place this question here. Even though everyone says there is no tricks to learning math. The only thing there is is hardwork.
As you might have known, trig involves a lot of memorizing. Something I really have problem memorizing is half and double formulas. But generally, I would like to find out the derivations of the formula to help me in memorizing those formulas.
Are there better ways? In case even the derivation is hard to understand.
Do you know any sources of trig practice problem? Something I have discovered is that practicing is only part of what really help you with math. So if you have any recommendation of books to read, please put it here.
How much time a day do you guys spend on practice? This is my final question.