If $\alpha +\beta +\gamma =2\pi ,$ then [IIT 1979]

Question

Accepted Answer

$	an \frac{\alpha }{2}+	an \frac{\beta }{2}+	an \frac{\gamma }{2}=	an \frac{\alpha }{2}	an \frac{\beta }{2}	an \frac{\gamma }{2}$

Answer

$	an \frac{\alpha }{2}	an \frac{\beta }{2}+	an \frac{\beta }{2}	an \frac{\gamma }{2}+	an \frac{\gamma }{2}	an \frac{\alpha }{2}=1$

Answer

$	an \frac{\alpha }{2}+	an \frac{\beta }{2}+	an \frac{\gamma }{2}=-	an \frac{\alpha }{2}	an \frac{\beta }{2}	an \frac{\gamma }{2}$

Answer

None of these

trigonometry