If A+B+C=2S, then prove that `cos(S-A)+cos(S-B)+cosC=-1+4cos((S-A)/2)cos((S-B)/2)cos(C/2)`

If A+B+C=2S, then prove that cos(S-A)+cos(S-B)+cos C=-1+4cos((S-A)/(2))cos((S-B)/(2))cos((C)/(2))

IF A+B+C=2S, then prove that cos(S-A)+cos(S-B)+cosC=-1+4cos""(S-A)/2cos""(S-B)/2cos""C/2 .

If A+B+C=2S then prove that the following: cos(S-A)+cos(S-B)+cosC =4cos((S-A)/2)cos((S-B)/2)cosC/2-1

If A+B+C = 2S , then prove that sin(S-A)+sin(S-B)+sinC = 4 cos ((S-A)/2) cos ((S-B)/2) sin C/2 .

If A+B+C = 2S , then P.T cos(S-A)+cos(S-B)+cos(S-C)+cosS=4cos.(A)/(2)cos.(B)/(2)cos.(C)/(2)

If A,B,C are the angles of a triangle then prove that cos A+cos B-cos C=-1+4cos((A)/(2))cos((B)/(2))sin((C)/(2))

If A +B+C= 2S , then prove that (i) sin (S-A)+sin (S-B) + sin C=4 cos . (S-A)/(2) cos. (S-B)/(2) sin .(C)/(2) (ii) cos (S-A)+cos (S-B)+cos C=-1+4 cos. (S-A)/(2) cos.(S-B)/(2)cos. (C)/(2)

Prove that a cos A+b cos B+c cos C<=s

If A+B+C=180^@ , then prove that cos2A + cos2B +cos2C=-1-4cosA cosB cosC .

If A,B,C are the angles of a triangle then prove that cosA+cosB-cosC=-1+4cos(A/2)cos(B/2)sin(C/2)