Parabola: Tangents to the Endpoints of a Focal Chord

This sketch corresponds to p.840 #15 and shows the conclusions proven in part a, b and c. You can drag point to see other possible focal chords. Notice the conclusions: a) The tangent lines at and are perpendicular b) The tangent lines meet on the directrix. In this diagram, their point of intersection is labeled c) The segment is perpendicular to the focal chord Use the checkboxes to show/hide the various features of the graph