The curve is drawn so that the ratio parameter above

is the ratio of the distances from the curve point

to the center of the circles and to the thick line

at the right. The center point is called focal point,

the line is called directrix.

If this ratio equals 1, then we have a Parabola.

If one interpretes the circles as level lines of a

cone and the lines as the level lines of a plane

such that equal colors indicate the same height,

then one recognizes the curve as the intersection of

a plane and a cone. It is a Conic Section, and the

above construction is a property of conic sections.

is the ratio of the distances from the curve point

to the center of the circles and to the thick line

at the right. The center point is called focal point,

the line is called directrix.

If this ratio equals 1, then we have a Parabola.

If one interpretes the circles as level lines of a

cone and the lines as the level lines of a plane

such that equal colors indicate the same height,

then one recognizes the curve as the intersection of

a plane and a cone. It is a Conic Section, and the

above construction is a property of conic sections.