With the help of these two formulas, sin^2 and cos^2 can be reduced to first-power cosines, which is something that's really helpful if: 1) you have to do really hard trig proofs, or 2) integrate a sine^2.

OOPS! To create playlists you must logged in.

If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)