EntityQ12094381· pop 7· linked from 81 articlesharmonic quadrilateralSign in to savecyclic quadrangle in which the products of the lengths of opposite sides are equalConnectionsquadrilateralEntityparallelogramEntitytrapezoidEntitygeometryEntitytriangleEntityInternational Standard Book NumberEntitycircleEntitysquareEntityrectangleEntitypolygonEntityrhombusEntitypentagonEntityEuclidean geometryEntityhexagonEntityright triangleEntityequilateral triangleEntityline segmentEntityoctagonEntityheptagonEntityJSTOROrganizationCategoriesTypes of quadrilaterals