# Comments on geometry task about proof for the inscribed angle? (what ties the steps together as a whole)

In this task you are going to work with certain type of proof for the (inscribed angel sentence?). The proof has three steps, as illustrated below. On the figures we have used (all those fancy greek letters). The inscribed angle sentence says $\alpha = \frac{\beta}{2}$. Write an explanation for the proof. Try to convey the idea behind each step, and after that the proof as a whole.
$180-2\alpha$
$\beta = 180 - (180 -2\alpha)$
$\alpha = \frac{\beta}{2}$
They are giving you the proof of three cases: the first two with $\,\alpha\,$ an acute angle and the last one with it an obtuse one. The first case is then subdivided in two cases: one of the angle's legs is a diameter, and then none of the legs is a diameter...I think this pretty much covers all the cases, doesn't it? –  DonAntonio Oct 17 '12 at 13:16