Question

In triangle $ABC$ $a,b,c$ are the length of its sides and $A,B,C$ are the angles of triangle $ABC$. The correct relation is given by

• A. $(b-c)\sin \left(\frac{B-C}{2}\right)=a\cos \frac{A}{2}$
• B. $(b-c)\cos \left(\frac{A}{2}\right)=a\sin \frac{B-C}{2}$
• C. $(b+c)\sin \left(\frac{B+C}{2}\right)=a\cos \frac{A}{2}$
• D. $(b-c)\cos \left(\frac{A}{2}\right)=a\sin \frac{B+C}{2}$

Answer 1

The correct option is B $(b-c)\cos \left(\frac{A}{2}\right)=a\sin \frac{B-C}{2}$