The trapezoid ABCD, of bases AB and CD, is inscribed in a circumference Γ. Let X a variable point of the arc AB of Γ that does not contain C or D. We denote Y to the point of intersection of AB and DX, and let Z be the point of the segment CX such that XCXZ=ABAY . Prove that the measure of ∠AZX does not depend on the choice of X. trapezoidisoscelesCyclicfixedanglegeometry