Limits Using Trig Identities

Hello everyone,

I am an independent learner who is taking on the differential calculus course. I took precalculus and trigonometry in high school, but I am struggling with the unit on trig identities because it's been a while since I've used trig and my understanding is a little shaky.

How important is trig for differential calc? Should I go back to the trigonometry course and review everything before continuing, or is it all right to have a gap in my knowledge here? How important is a super solid trig foundation for learning differential calc?

Thanks everyone!