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  2. Principal axis theorem - Wikipedia

    en.wikipedia.org/wiki/Principal_axis_theorem

    In geometry and linear algebra, a principal axis is a certain line in a Euclidean space associated with a ellipsoid or hyperboloid, generalizing the major and minor axes of an ellipse or hyperbola. The principal axis theorem states that the principal axes are perpendicular , and gives a constructive procedure for finding them.

  3. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    The line segments that are delimited on the axes of symmetry by the ellipsoid are called the principal axes, or simply axes of the ellipsoid. If the three axes have different lengths, the figure is a triaxial ellipsoid (rarely scalene ellipsoid), and the axes are uniquely defined.

  4. Ellipse - Wikipedia

    en.wikipedia.org/wiki/Ellipse

    An ellipse (red) obtained as the intersection of a cone with an inclined plane. Ellipse: notations Ellipses: examples with increasing eccentricity. In mathematics, an ellipse is a plane curve surrounding two focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant.

  5. Matrix representation of conic sections - Wikipedia

    en.wikipedia.org/wiki/Matrix_representation_of...

    By the principal axis theorem, the two eigenvectors of the matrix of the quadratic form of a central conic section (ellipse or hyperbola) are perpendicular (orthogonal to each other) and each is parallel to (in the same direction as) either the major or minor axis of the conic.

  6. Semi-major and semi-minor axes - Wikipedia

    en.wikipedia.org/wiki/Semi-major_and_semi-minor_axes

    The semi-minor axis of an ellipse runs from the center of the ellipse (a point halfway between and on the line running between the foci) to the edge of the ellipse. The semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the major axis that connects two points on the ellipse's edge. The semi ...

  7. Confocal conic sections - Wikipedia

    en.wikipedia.org/wiki/Confocal_conic_sections

    By the principal axis theorem, the plane admits a Cartesian coordinate system with its origin at the midpoint between foci and its axes aligned with the axes of the confocal ellipses and hyperbolas. If c {\displaystyle c} is the linear eccentricity (half the distance between F 1 {\displaystyle F_{1}} and F 2 {\displaystyle F_{2}} ), then in ...

  8. 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).

  9. List of centroids - Wikipedia

    en.wikipedia.org/wiki/List_of_centroids

    a, b = the principal semi-axes of the base ellipse c = the principal z-semi-axe from the center of base ellipse Solid paraboloid around z-axis: a, b = the principal semi-axes of the base ellipse c = the principal z-semi-axe from the center of base ellipse