Question

cos2 (x-y/2) - sin2 (x+y/2) = cosx.cosy

Answer 1

you want to proove it ?!

Answer 2

!??

Answer 3

This?
\[\cos^2(x-y/2)-\sin^2(x+y/2) = \cos(x) \cos(y)\]

Or this?
\[\cos^2(\frac{x-y}{2})-\sin^2(\frac{x+y}{2}) = \cos(x) \cos(y)\]


And was there a question here? Are you solving for x, y, or what? The first equation does have two y solutions, a \(\pm\) constant

Answer 4

Also given the level of difficulty with equations like this, please remember that on computers to show exponents you'll need to make use of the ^ symbol.

i.e. x^2 = x\(^2\)
x^(1/2) = x\(^{1/2}\) = \(\sqrt{\text{x}}\)

Answer 5

cos2 = cos(2) \(\approx -0.4161468365\)