Sum and Difference Formulas

 $\cos^2u-\sin^2u$  

 $2\cos^2u-1$  

 $1-2\sin^2u$  

 $1-\sin^2u$  

 $\sin^2u-\cos^2u$  

$\frac{\sin\ u}{1+\cos\ u}$

$\frac{\cos\ u}{1+\sin u}$

$\frac{1+\cos u}{\sin u}$

$\frac{\sin u}{1-\cos u}$

$\frac{1+\sin u}{\cos u}$

$\frac{2\tan u}{1-\tan^2u}$

$\frac{\tan^2u}{1+\tan u}$

$\frac{2\tan u}{1+\tan^2u}$

$\frac{\tan^2u}{1-\tan u}$

$\pm\sqrt{\frac{1-\cos u}{2}}$

$\pm\sqrt{\frac{1+\cos u}{2}}$

$\pm\sqrt{\frac{1+\sin u}{\cos u}}$

$\pm\sqrt{\frac{1-\sin u}{\cos u}}$

$\pm\sqrt{\frac{1+\cos u}{2}}$

$\pm\sqrt{\frac{1-\sin u}{2}}$

$\pm\sqrt{\frac{1+\sin u}{\cos u}}$

$\pm\sqrt{\frac{1-\cos u}{\sin u}}$