Ellipses

thumb|An ellipse (red) obtained as the intersection of a cone with an inclined plane. thumb|Ellipses: examples with increasing eccentricity

300px|thumb|Examples of superellipses for , .

thumb|Trammel of Archimedes animated model

two-dimensional orthogonal coordinate system

an ellipse defined from a triangle, tangent to its sides at their midpoints

class of second-order linear partial differential equations

circumellipse of a triangle whose center is the triangle's centroid

thumb|right|300px|Examples of 3-ellipses for three given foci. The progression of the distances is not linear.