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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. 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.

  4. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    Given: Ellipsoid ⁠ x 2 / a 2 ⁠ + ⁠ y 2 / b 2 ⁠ + ⁠ z 2 / c 2 ⁠ = 1 and the plane with equation n x x + n y y + n z z = d, which have an ellipse in common. Wanted: Three vectors f 0 (center) and f 1, f 2 (conjugate vectors), such that the ellipse can be represented by the parametric equation

  5. 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.

  6. Elliptic curve - Wikipedia

    en.wikipedia.org/wiki/Elliptic_curve

    Given the curve y 2 = x 3 + bx + c over the field K (whose characteristic we assume to be neither 2 nor 3), and points P = (x P, y P) and Q = (x Q, y Q) on the curve, assume first that x P ≠ x Q (case 1). Let y = sx + d be the equation of the line that intersects P and Q, which has the following slope: =

  7. Dual curve - Wikipedia

    en.wikipedia.org/wiki/Dual_curve

    Eliminating p, q, r, and λ from these equations, along with Xp + Yq + Zr = 0, gives the equation in X, Y and Z of the dual curve. On the left: the ellipse (⁠ x / 2 ⁠) 2 + (⁠ y / 3 ⁠) 2 = 1 with tangent lines xX + yY = 1 for any X, Y, such that (2X) 2 + (3Y) 2 = 1. On the right: the dual ellipse (2X) 2 + (3Y) 2 = 1. Each tangent to the ...

  8. Eccentricity (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Eccentricity_(mathematics)

    The linear eccentricity of an ellipse or hyperbola, denoted c (or sometimes f or e), is the distance between its center and either of its two foci. The eccentricity can be defined as the ratio of the linear eccentricity to the semimajor axis a : that is, e = c a {\displaystyle e={\frac {c}{a}}} (lacking a center, the linear eccentricity for ...

  9. Curve fitting - Wikipedia

    en.wikipedia.org/wiki/Curve_fitting

    The first degree polynomial equation = + is a line with slope a. A line will connect any two points, so a first degree polynomial equation is an exact fit through any two points with distinct x coordinates. If the order of the equation is increased to a second degree polynomial, the following results: