Trigonometric Identities

The times they are a-changin’.

This post seems to be older than 14 years—a long time on the internet. It might be outdated.

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 7:30 6:30.

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