Question

if a+b+c=180 then prove that cos A+ cos B - cos C = -1 + 4 cos A/2 . cos B/2 . sin C/2

Answer 1

Answer:

a+v+g

Step-by-step explanation:

if a+b+c=180 then prove that cos A+ cos B - cos C = -1 + 4 cos A/2 . cos B/2 . sin C/2