On Quadrilaterals Given by Angles in the Isotropic Plane

In this paper, we study quadrilaterals $ABCD$ in the isotropic plane that are determined by the vertex angles α=∠(DA,AB), β=∠(AB,BC), γ=∠(BC,CD) and a diagonal angle ε=∠(AC,BD). We obtain the loci of diagonal points and the envelope of the sides when only some of the angles are given.