Characterizations of bicentric quadrilaterals - Martin Josefsson We will prove two conditions for a tangential quadrilateral to be cyclic. According to one of these, a tangential quadrilateral is cyclic if and only if its Newton line is perpendicular to the Newton line of its contact quadrilateral. ✪ ✪ ✪ ✪ ✪ Hidden Content: **Hidden Content: Content of this hidden block can only be seen by members of (usergroups: V.I.P Downloader).** Theo LTTK Education