High School Trigonometry/Half-Angle Identities

$\sin ^{2}{u}={\frac {1-\cos {2u}}{2}}$

$\cos ^{2}{u}={\frac {1+\cos {2u}}{2}}$

$\tan ^{2}{u}={\frac {1-\cos {2u}}{1+\cos {2u}}}$

This material was adapted from the original CK-12 book that can be found here. This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License