Second-level formula of conic eccentricity: e=c/a.

The eccentricity of the hyperbola: e=c/a (1, +∞) (c, half focal length; a, semi-major axis (ellipse)/semi-real axis (hyperbola)) in a conic section In the unified definition, the unified polar coordinate equation of a conic section (quadratic non-circular curve) is ρ=ep/(1-e×cosθ), where e represents the eccentricity and p is the distance from the focus to the directrix.

In these two conclusions

call ML a vertical line of a conic section, then the conclusion shows that the area of ??a square with the vertical line as the side length is equal to EM. Draw the area of ??a rectangle on one side. For an ellipse, EOEH, the rectangle EOXM exceeds the rectangle EHNM; while for a parabola, EO=EH, the rectangle EOXM exactly fills the rectangle EHNM.