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  2. Eccentricity (mathematics) - Wikipedia

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

    The eccentricity of an ellipse is, most simply, the ratio of the linear eccentricity c (distance between the center of the ellipse and each focus) to the length of the semimajor axis a. =. The eccentricity is also the ratio of the semimajor axis a to the distance d from the center to the directrix:

  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. Conic section - Wikipedia

    en.wikipedia.org/wiki/Conic_section

    the eccentricity can be written as a function of the coefficients of the quadratic equation. [18] If 4AC = B 2 the conic is a parabola and its eccentricity equals 1 (provided it is non-degenerate). Otherwise, assuming the equation represents either a non-degenerate hyperbola or ellipse, the eccentricity is given by

  5. Conic constant - Wikipedia

    en.wikipedia.org/wiki/Conic_constant

    In geometry, the conic constant (or Schwarzschild constant, [1] after Karl Schwarzschild) is a quantity describing conic sections, and is represented by the letter K. The constant is given by K = − e 2 , {\displaystyle K=-e^{2},} where e is the eccentricity of the conic section.

  6. Orbital eccentricity - Wikipedia

    en.wikipedia.org/wiki/Orbital_eccentricity

    For elliptical orbits, a simple proof shows that ⁡ yields the projection angle of a perfect circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury (e = 0.2056), one must simply calculate the inverse sine to find the projection angle of 11.86 degrees. Then, tilting any circular object by that angle ...

  7. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    Hence, it is confocal to the given ellipse and the length of the string is l = 2r x + (a − c). Solving for r x yields r x = ⁠ 1 / 2 ⁠ (l − a + c); furthermore r 2 y = r 2 x − c 2. From the upper diagram we see that S 1 and S 2 are the foci of the ellipse section of the ellipsoid in the xz-plane and that r 2 z = r 2 x − a 2.

  8. Focus (geometry) - Wikipedia

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

    A conic is defined as the locus of points for each of which the distance to the focus divided by the distance to the directrix is a fixed positive constant, called the eccentricity e. If 0 < e < 1 the conic is an ellipse, if e = 1 the conic is a parabola, and if e > 1 the conic is a hyperbola.

  9. Angular eccentricity - Wikipedia

    en.wikipedia.org/wiki/Angular_eccentricity

    Angular eccentricity α (alpha) and linear eccentricity (ε). Note that OA=BF=a. Angular eccentricity is one of many parameters which arise in the study of the ellipse or ellipsoid. It is denoted here by α (alpha). It may be defined in terms of the eccentricity, e, or the aspect ratio, b/a (the ratio of the semi-minor axis and the semi-major ...