Confused on what should be negative when finding with half angle identities

I have to memorize over 30 Trigonometric identities and additional stuff. How can I do it? : r/learnmath

Rules for Aromaticity: The 4 Key Factors – Master Organic Chemistry

I am trying to find the work done by gravity for the mass sliding up an inclined plane. I am confused why I don't include the y component of gravity (mgcostheta) in

Is it possible that the value of sin is negative in a half angle formula? - Quora

Half Angle Formula, Quadrant Rule & Examples

2. From Snell's law to Vergence formula - Docteur Damien Gatinel

Half Angle Formula, Quadrant Rule & Examples

Half-angle identitiespositive or negative?

Breakdown voltage. Does anyone happen to know how to find the breakdown voltage (Vz) of the graph, I'm a little confused thank you! : r/AskElectronics

How to Solve Half-Angle Identities? (7+ Awesome Examples!)

Can you find sin720°, cos720°, tan720°, cot720° by using the double angle identities for 360°? - Quora

half angle formulas

Half Angle Formula, Quadrant Rule & Examples