Question

If A+B+C=180 prove that sin2A +sin2B-sin2C = 4cosA cosB sinC

Answer 1

Step-by-step explanation:

2sin(a+b)cos(a-b)-2sin c cos c

2sin c cos(a-b)-2sin c cos c

2sin c (cos(a-b)-cos c)

2sin c(cos[(a-b)+cos(a+b)]=4cos Acos B sin c

2sin c(2cosA cosB)