Unknown008
Dec 9, 2010, 07:00 AM
If this is what you are trying to prove:
\cos^2\(\frac{A}{2}\)\cos^2\(\frac{B}{2}\)\cos^2\( \frac{C}{2}\) \equiv 2 + 2\sin\(\frac{A}{2}\)\sin\(\frac{A}{2}\)\sin\(\frac {A}{2}\)
I don't see how they are equivalent...
cos is always less than 1. Hence, the left hand side is less than 1.
On the right hand side, you have 2 + 2sin sin sin
sin is less than 1, and twice that isn't much... the '2' in front of everything makes it too much.