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  2. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    The reverse scaling (see above) transforms the unit sphere back to the ellipsoid and the vectors e 0, e 1, e 2 are mapped onto vectors f 0, f 1, f 2, which were wanted for the parametric representation of the intersection ellipse. How to find the vertices and semi-axes of the ellipse is described in ellipse.

  3. Rytz's construction - Wikipedia

    en.wikipedia.org/wiki/Rytz's_construction

    The Rytz’s axis construction is a basic method of descriptive geometry to find the axes, the semi-major axis and semi-minor axis and the vertices of an ellipse, starting from two conjugated half-diameters. If the center and the semi axis of an ellipse are determined the ellipse can be drawn using an ellipsograph or by hand (see ellipse).

  4. Vertex (curve) - Wikipedia

    en.wikipedia.org/wiki/Vertex_(curve)

    An ellipse (red) and its evolute (blue). The dots are the vertices of the curve, each corresponding to a cusp on the evolute. In the geometry of plane curves, a vertex is a point of where the first derivative of curvature is zero. [1]

  5. Four-vertex theorem - Wikipedia

    en.wikipedia.org/wiki/Four-vertex_theorem

    An ellipse (red) and its evolute (blue), showing the four vertices of the curve, each vertex corresponding to a cusp on the evolute.. The curvature at any point of a smooth curve in the plane can be defined as the reciprocal of the radius of an osculating circle at that point, or as the norm of the second derivative of a parametric representation of the curve, parameterized consistently with ...

  6. Focal conics - Wikipedia

    en.wikipedia.org/wiki/Focal_conics

    A,C: vertices of the ellipse and foci of the hyperbola E,F: foci of the ellipse and vertices of the hyperbola Focal conics: two parabolas A: vertex of the red parabola and focus of the blue parabola F: focus of the red parabola and vertex of the blue parabola. In geometry, focal conics are a pair of curves consisting of [1] [2] either

  7. Vertex (geometry) - Wikipedia

    en.wikipedia.org/wiki/Vertex_(geometry)

    In geometry, a vertex (pl.: vertices or vertexes) is a point where two or more curves, lines, or edges meet or intersect. As a consequence of this definition, the point where two lines meet to form an angle and the corners of polygons and polyhedra are vertices.

  8. Radius of curvature - Wikipedia

    en.wikipedia.org/wiki/Radius_of_curvature

    An ellipse (red) and its evolute (blue). The dots are the vertices of the ellipse, at the points of greatest and least curvature. For a semi-circle of radius a in the lower half-plane =. The circle of radius a has a radius of curvature equal to a.

  9. Elliptic geometry - Wikipedia

    en.wikipedia.org/wiki/Elliptic_geometry

    The name "elliptic" is possibly misleading. It does not imply any direct connection with the curve called an ellipse, but only a rather far-fetched analogy. A central conic is called an ellipse or a hyperbola according as it has no asymptote or two asymptotes.