Equilic quadrilateral is a
quadrilateral ABCD with one pair of opposite sides equal (AB =
CD) and the sum of angles A and D equal to 120°.
Reference: Garfunkel, J.
"The Equilic Quadrilateral." Pi Mu Epsilon J. 7, 317-329, 1981.
The following visual
illustrations show the result of exploring equilic
quadrilateral with dynamic geometry software.