Topic explanation

Standard explanation

A conic is defined by a focus-directrix ratio e; ellipse has e<1, parabola e=1, hyperbola e>1.

Key points

• Conics and eccentricity
• rule
• worked example
• Conics and eccentricity: A conic is defined by a focus-directrix ratio e; ellipse has e<1, parabola e=1, hyperbola e>1.
• CONCEPT AND RULE: A conic is defined by a focus-directrix ratio e; ellipse has e<1, parabola e=1, hyperbola e>1.
• METHOD: For conics and eccentricity, identify the given information and required result. Select the matching
• A conic is defined by a focus-directrix ratio e; ellipse has e<1, parabola e=1, hyperbola e>1.
• Worked pattern: The locus PF=e times distance to the directrix classifies the conic.

Labelled diagram