Conic Section

The locus of a point moving on a plane such that its distances from a fixed point and a fixed straight line on the plane are in constant ratio e, is called a conic.

The fixed point is called the focus and is usually denoted by S. The fixed straight line is called the directrix. The constant ratio e is called the eccentricity. The straight line on the plane passing through the focus and perpendicular to the directrix is called the axis. Therefore, the locus of a point moving on a plane such that SP/ P M = e , where PM is the perpendicular distance from p to the directrix, is called a conic.

• if e= 1 the conic is called a parabola
• if 0 <1>the conic is called an ellipse
• if e> 1 the conic is called a hyperbola.