An isoscelestriangle ABC , ABN AC, is inscribed in a circle Achord AD intersects BC at E. Prove that AC is tangent at C to the circle that circumscribes ACED. ( Hint : use the theorem that the angle formed by a tangent and a chord is congruent to the inscribed angle subtending the Chord. The converse if also true: congruence of angles implies the tangency. ) B