Question

If A + B + C = π, prove that CosA / SinB * SinC + CosB / SinC * SinA + CosC + SinA *SinB= 2

Answer 1

assume A=B=C= 60 then you get the results same....for proof use formulae of
sinA+sinB= 2sin(A+B/2)Cos(A-B/2)