For any triangle ABC, prove that a+b = cos A-B/2
2 sin c/2
Do you mean
Mollweide's Formula ?\((a+b)\sin\frac{C}{2}=c \cdot cos\left(\frac{A-B}{2}\right) \)
For any triangle ABC, prove that
\(\frac{a+b}{2}=\frac{cos(A-\frac{B}{2})}{sin(\frac{C}{2})}\)