Thread: Trig Prove

sinn2a + sin2b = 2sin(a+b)cos(a-b)
=2sinc{cos(a-b)}

lhs becomes
=2sinc{cos(a-b)} + sin2c
=2sinc{cos(a-b) + cosc}
=2sinc{cos(a-b) - cos(a+b)}
=4sina.sinb.sinc=rhs