Originally Posted by

**Paze** Hi MHF. If anyone has time, I would love for concrete proof for the following trig functions:

$\displaystyle sin(u+v)=sin(u)\cdot cos(v)+cos(u)\cdot sin(v)\\sin(u-v)=sin(u)\cdot cos(v)-cos(u)\cdot sin(v)\\cos(u+v)=cos(u)\cdot cos(v)-sin(u)\cdot sin(v)\\cos(u-v)=cos(u)\cdot cos(v)+sin(u)\cdot sin(v)\\sin(2u)=2\cdot sin(u)\cdot cos(u)\\cos(2u)=cos^2(u)-sin^2(u)\\sin^2(u)+cos^2(u)=1$

I do know the last one but I thought I'd have it here to have the whole bulk for search engines etc. in case of a good answer on the thread.

Thanks a lot!