Question

Q8 (a) If A, B and C are interiors angles of a triangles AABC
COS A+B
Show that
2
sinc
2

Answer 1

Answer:

sum of interior angles = 180

A+B+C = 180

A+B = 180-C

divide by '2' on both sides

(A+B)/2 = (180-C) /2

applying cos on both sides

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

cos (A+B)/2 = sin C/2