- #1
tweety1234
- 112
- 0
Homework Statement
Can someone please explain how my book got [itex] sin^{2} \theta = \frac{1-cos2\theta}{2} [/itex] and [itex] cos^{2}\theta = \frac{1+cos2\theta}{2} [/itex]
As I thought the half angle formula's were [itex] sin \frac{\theta}{2} = \sqrt{\frac{1-cos\theta}{2}} [/itex]
[itex] cos\frac{\theta}{2} = \sqrt\frac{1+cos\theta}{2}} [/itex]
So how can it also be the top one's aswell?
Thanks.