Question

how would verify this identity? :
cos(u)cos(v)=(1/2)(cos(u-v)+cos(u+v)

Answer 1

I have no idea lol.

Answer 2

using trig properties, sum and difference formulas
\[\cos(u+v) = \cos u*\cos v - \sin u*\sin v\]
\[\cos(u-v) = \cos u*\cos v + \sin u*\sin v\]
therefore
\[\cos(u-v) + \cos(u+v) = 2\cos u*\cos v\]

Answer 3

oh really now

Answer 4

haha yes really