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

A + B + C = 2S then prove that cos (SA) + cos (SB) + cos (SC) + cos S = 4 (cos A) / (2) (cos B) / (2) (cos C) / (2)

If A+B+C=0 , then prove that cos ^(2)A+ cos ^(2) B + cos ^(2) C =1+2 cos A cos B cos C

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 .

Prove that: cos(A+B+C)+cos(A-B+C)+cos(A+B-C)+cos(-A+B+C)=4cos A cos B cos C

If A+B +C =2S, prove that : cos^2 S + cos^2 (S- A) + cos^2 (S-B)+ cos^2 (S -C) = 2 +2 cos A cos B cos C .

If A+B+C=2S , prove that : cos^2 S + cos^2 (S-A) + cos^2 (S-B) + cos^2 (S-C) = 2+2cosA cosB cosC .

If A+B+C=2S , prove that : cos^2 S + cos^2 (S-A) + cos^2 (S-B) + cos^2 (S-C) = 2+2cosA cosB cosC .

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= pi/2 ,prove that cos(A - B - C)+ cos (B-C- A) + cos (C- A - B)= 4 cos A cos B cos C

Prove that: cos(A+B+C)+cos(A-B+C)+cos(A+B-C)+cos(-A+B+C)=4cos A\ cos B\ cos C