Question

( sum sin A sin (B-c)=0 )
on ( Delta A B C )
( A+B+C=pi )
( A=pi-(B+C) )
( sum sin (B+C) sin (B-C) )
( =sum_{S 17}left(31 n^{2} B-operatorname{Sin}^{2} Cright) )
( =0 )
( therefore ) Hence Proved

# Prove that in a triangle ABC, sin Asin(B-C)= 0.

Solution