1.

Sin(S-A) + sin(S-B) + sin(S-C) - sinS = 1 - cos2A - cos2B - cos2C +2cosAcosBcosC​

Answer» ONG>ANSWER:

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)


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