Assertion: parabola's line | /r/HasProperty | the directrix of the parabola
Facets:
Source sentences:
text: A parabola is a plane curve, every point of which has the property that the distance to a fixed point (called the focus of the parabola ) is equal to the distance to a straight line (the directrix of the parabola ).
text: The line is called the directrix of the parabola and the point the focus of the parabola.