Assertion: ellipse's axis | /r/HasProperty | the directrix
Facets:
Source sentences:
text: Each focus F of the ellipse is associated to a line D perpendicular to the major axis (the directrix) such that the distance from any point on the ellipse to F is a constant fraction of its distance from D.
text: Each focus $ F $ of the ellipse is associated to a line $ D $ perpendicular to the major axis (the directrix) such that the distance from any point on the ellipse to $ F