Eigenschafter gewisser Vierecke, die axialsymmetrischen Bereichen um- bzw. einbeschrieben sind (Q789730)

Given a smooth bounded convex region B in the plane which is symmetric about an axis s this paper considers properties of two types of quadrangles: The U-quadrangles are circumscribed, and their sides support B in their midpoints; the E-quadrangles are inscribed, and the line of support to B at each vertex is parallel to the diagonal not containing the vertex in question. In particular, any such quadrangle that does not have s as an axis of symmetry, has exactly two of its vertices in each of the open halfplanes determined by s.