Focal chordsThe pole P of a focal chord H_{1}H_{2} lies on the directrix. The connection of the pole P with the focus F_{1} is perpendicular to the chord:The second focus F_{2} is reflected in the tangents at H_{1} and H_{2} to T_{1}[F_{2}] and T_{2}[F_{2}]. The two points are equally distant from P and equally distant from F_{1}. Hence PF_{1} is perpendicular to T_{1}T_{2} Kapitel und Portal |
Circle of reflexion Perpendicular chords |