1. ## Triangle Prove

For any triangle, show that cos(Y/2) = sqrt{[2(2 - c)]/(ab)}
where s = (a + b + c).

Hint Given:

Use the Half-angle Formula and the Law of Cosines.

2. Originally Posted by magentarita
Use the Half-angle Formula and the Law of Cosines.
Why do you post if you know what to do ?

3. Originally Posted by magentarita
For any triangle, show that cos(Y/2) = sqrt{[2(2 - c)]/(ab)}
where s = (a + b + c).

Hint Given:

Use the Half-angle Formula and the Law of Cosines.
I'll bite. What's Y? And where does the s come into the equation?

-Dan