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  2. Perimeter of an ellipse - Wikipedia

    en.wikipedia.org/wiki/Perimeter_of_an_ellipse

    An ellipse has two axes and two foci. Unlike most other elementary shapes, such as the circle and square, there is no algebraic equation to determine the perimeter of an ellipse. Throughout history, a large number of equations for approximations and estimates have been made for the perimeter of an ellipse.

  3. Principal axis theorem - Wikipedia

    en.wikipedia.org/wiki/Principal_axis_theorem

    The equation is for an ellipse, since both eigenvalues are positive. (Otherwise, if one were positive and the other negative, it would be a hyperbola.) The principal axes are the lines spanned by the eigenvectors. The minimum and maximum distances to the origin can be read off the equation in diagonal form.

  4. Elliptic coordinate system - Wikipedia

    en.wikipedia.org/wiki/Elliptic_coordinate_system

    The classic applications of elliptic coordinates are in solving partial differential equations, e.g., Laplace's equation or the Helmholtz equation, for which elliptic coordinates are a natural description of a system thus allowing a separation of variables in the partial differential equations. Some traditional examples are solving systems such ...

  5. 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.

  6. Elliptic equation - Wikipedia

    en.wikipedia.org/wiki/Elliptic_equation

    An elliptic equation can mean: The equation of an ellipse; An elliptic curve, describing the relationships between invariants of an ellipse; A differential equation with an elliptic operator; An elliptic partial differential equation

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

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

    The semi-major axis (major semiaxis) is the longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus, and to the perimeter. The semi-minor axis (minor semiaxis) of an ellipse or hyperbola is a line segment that is at right angles with the semi-major axis and has one end at the center of the conic section.

  8. Elliptic curve - Wikipedia

    en.wikipedia.org/wiki/Elliptic_curve

    This equation is not defined on the line at infinity, but we can multiply by to get one that is : Z Y 2 = X 3 + a Z 2 X + b Z 3 {\displaystyle ZY^{2}=X^{3}+aZ^{2}X+bZ^{3}} This resulting equation is defined on the whole projective plane, and the curve it defines projects onto the elliptic curve of interest.

  9. Superellipse - Wikipedia

    en.wikipedia.org/wiki/Superellipse

    Examples of superellipses for =, =. A superellipse, also known as a Lamé curve after Gabriel Lamé, is a closed curve resembling the ellipse, retaining the geometric features of semi-major axis and semi-minor axis, and symmetry about them, but defined by an equation that allows for various shapes between a rectangle and an ellipse.