Half Angle Formulas-Cos,Sin,Tan

In the first part of the video, I cover how to where they come from and the second half I will cover how to solve.
Here are the formulas:
the sin of a half-angle = plus or minus of the square root of 1 minus cos u over 2
the cosine of a half angle = plus or minus the square root of 1 + cosine u over 2

This video goes with following Math Standard: Prove and apply trigonometric identities.
Prove addition, subtraction, double and half-angle formulas for sine, cosine, and tangent and use them to solve problems.
Georgia Math Standard, MGSE9-12.F.TF.9

Everything you need to know about Trig Identities Playlist
https://www.youtube.com/playlist?list=PLurjkZV1ykGYVZxjQFw8O2F30yxh-CeD-