Geometry proofs question, help please?!?

ABCE is a cyclic quadrilateral. The four points lie on a circle, but not the circle shown. <7 is a right angle since it is inscribed in a semicircle, and <2 is a right angle since CE is perpendicular to BD. Since two right angles are supplementary and since the angles of any quadrilateral add up to 360�, the other pair of angles is also supplementary. Any quadrilateral with opposite angles supplementary is cyclic. QED