Question

A+B+C=2s then cos²s+cos²(s-A)+cos²(s-B)+cos²(s-c)​

Answer 1

The answer is in attachment

thank you

Answer 2

sinS+sin(S-A)+sin(S-B)-sin(S-C)

{sinS-sin(S-C)}+{sin(S-A)+sin(S-B)}

2cos(2S-C)/2sin(C/2)+2sin(C/2)cos(B-A)/2

=2sinC/2[cos(A+B)/2 +cos(B-A)/2]

=2sinC/2 .[2cos(B/2)cos(A/2)]

=4cos(A/2)cos(B/2)sin(C/2)