X = a 2/c (focus (c,0))
X =-a 2/c (focus (-c, o))
Let the alignment be x = f.
Then the distance l from a to a straight line is f-X.
Let af1/l = e.
(x-c)? +y? =e? (f-x)?
Simplify (1-e? )x? -2xc+c? +y? -e? f? +2e? fx=0
Make 2c=2e? f
So f=c/e?
Let this point be the right vertex rule (c/e? -a)e=a-c
When e=c/a, the above formula holds.
So f=a? /c
The equation is (1-e? )x? +y? =e? f? -c?
Introduction to ellipse
In mathematics, an ellipse is a curve around two focal points on a plane, so for each point on the curve, the sum of the distances to the two focal points is constant. Therefore, it is a generalization of a circle, and it is a special type of ellipse with two focuses at the same position. The shape of an ellipse (how to "stretch") is expressed by its eccentricity, which can be any number from 0 (the limit case of a circle) to close to but less than 1.
An ellipse is a closed cone section: a plane curve intersects a plane through a cone. There are many similarities between the other two forms of ellipse and cone section: parabola and hyperbola, which are both open and unbounded. The cross section of a cylinder is elliptical unless it is parallel to the axis of the cylinder.