Question

In ∆ABC sin(B+C)/2=?​

Answer 1

Answer:

CosA/2

Step-by-step explanation:

In ∆ABC A+B+C= 180°

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

= Sin(180-A)/2

= Sin(90°-A/2)

= Cos(A/2)