Prove $\sin\alpha \cos\alpha + \sin\beta \cos\beta + \sin\gamma \cos\gamma = 2\sin\alpha \sin\beta \sin\gamma$, where $\alpha + \beta + \gamma = \pi$
Prove that $\sin(2A)+\sin(2B)+\sin(2C)=4\sin(A)\sin(B)\sin(C)$ when $A,B,C$ are angles of a triangle