Question

plzz guys solve this some coudn't solve it i need your help plzz help​

Answer 1

Answer:

A,B,C are interior angles of triangle ABC

1. Sin[ B+C/2] = CosA/2
2. A+B+C = 180°
3. B+C= 180- A
4. B+C = 90- A/2

Sin( B+C/2) = Sin( 90-A/2)

Sin(B+C/2) = Cos A/2