Question

what is the diretrix of a parabola?

Answer 1

The directrix is a line that the parabola , " curves away " from.

For a fixed point, F, called the focus, and a line, called the directrix, not thru the focus, a parabola is the set of all points in the plane with the following property: The distance from any point X on the parabola to the focus F = distance from that same point X to the directrix [ the shortest distance to the directrix ]

Think of the parabola as containing the focus " inside" of it, and the directrix, " directing" the parabola away from it....like two North poles of a magnet repel each other as they are moved closer together.

For a simple parabola, like y = x ^ 2, the directrix would be at y = - 1/4 , and the focus is at ( 0, 1 / 4 ) , with the parabola opening upwards like a smile, with the focus inside it.

Answer 2

thanks

Answer 3

np