For all values of A, B and C, prove that:- cosA + cosB + cosC + cos (A+B+C)= 4cos (A + B/2). cos (B+C/2). cos (C+ A/2)

For all values of A, B and C, prove that:- cosA + cosB + cosC + cos (A

1.	For all values of A, B and C, prove that:- cosA + cosB + cosC + cos (A+B+C)= 4cos (A + B/2). cos (B+C/2). cos (C+ A/2)
Answer» For all values of A, B and C, prove that:- cosA + cosB + cosC + cos (A+B+C)= 4cos (A + B/2). cos (B+C/2). cos (C+ A/2)