In a triangle ABC, write cos (B+C/2) in terms of Angel a

1.	In a triangle ABC, write cos (B+C/2) in terms of Angel a
Answer» We know that,A+ B+ C = 180°B+C = 180° - ADividing both sides by 2 B+C /2 = 90° - A/2Taking cos on both sides,cos(B+C/2) = cos(90° - A/2)This gives,cos(B+C/2)= sin(A/2)

Discussion