Eccentricity : Eccentricity of an ellipse is ratio of distances from centre of ellipse to one of foci and to one of the vertices of ellipse ( eccentricity is denoted by e ) i . e ., e = c / a .
Standard equation of Ellipse :
Equation of an ellipse is simplest if centre of ellipse is at origin & foci are on x-axis or y-axis .