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  2. Matrix representation of conic sections - Wikipedia

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

    Then for the ellipse case of AC > (B/2) 2, the ellipse is real if the sign of K equals the sign of (A + C) (that is, the sign of each of A and C), imaginary if they have opposite signs, and a degenerate point ellipse if K = 0. In the hyperbola case of AC < (B/2) 2, the hyperbola is degenerate if and only if K = 0.

  3. Ellipse - Wikipedia

    en.wikipedia.org/wiki/Ellipse

    A circle viewed from a side angle looks like an ellipse: that is, the ellipse is the image of a circle under parallel or perspective projection. The ellipse is also the simplest Lissajous figure formed when the horizontal and vertical motions are sinusoids with the same frequency: a similar effect leads to elliptical polarization of light in ...

  4. Circle–ellipse problem - Wikipedia

    en.wikipedia.org/wiki/Circleellipse_problem

    Then, wherever a circle was used before, use an ellipse. A circle can already be represented by an ellipse. There is no reason to have class Circle unless it needs some circle-specific methods that can't be applied to an ellipse, or unless the programmer wishes to benefit from conceptual and/or performance advantages of the circle's simpler model.

  5. Conic section - Wikipedia

    en.wikipedia.org/wiki/Conic_section

    As above, for e = 0, the graph is a circle, for 0 < e < 1 the graph is an ellipse, for e = 1 a parabola, and for e > 1 a hyperbola. The polar form of the equation of a conic is often used in dynamics; for instance, determining the orbits of objects revolving about the Sun. [20]

  6. Flattening - Wikipedia

    en.wikipedia.org/wiki/Flattening

    A circle of radius a compressed to an ellipse. A sphere of radius a compressed to an oblate ellipsoid of revolution. Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution respectively. Other terms used are ellipticity, or oblateness.

  7. Ellipsoid - Wikipedia

    en.wikipedia.org/wiki/Ellipsoid

    Flattening, also called ellipticity and oblateness, is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid), respectively. Focaloid, a shell bounded by two concentric, confocal ellipsoids; Geodesics on an ellipsoid

  8. Focus (geometry) - Wikipedia

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

    The ellipse thus generated has its second focus at the center of the directrix circle, and the ellipse lies entirely within the circle. For the parabola, the center of the directrix moves to the point at infinity (see Projective geometry). The directrix "circle" becomes a curve with zero curvature, indistinguishable from a straight line.

  9. Generalized conic - Wikipedia

    en.wikipedia.org/wiki/Generalized_conic

    In mathematics, a generalized conic is a geometrical object defined by a property which is a generalization of some defining property of the classical conic.For example, in elementary geometry, an ellipse can be defined as the locus of a point which moves in a plane such that the sum of its distances from two fixed points – the foci – in the plane is a constant.