Wikipedia has a list of trig identities.
I’m not quite sure what’s worse, the fact that Wikipedia has them or the fact that I need to use them.
Calc III exam at
Here are the three I’ve been using a lot:
- Sin2[x] = (1-Cos[2x])/2
- Cos2[x] = (1+Cos[2x])/2
- Sin2[x] + Cos2[x] = 1