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  2. Quadric - Wikipedia

    en.wikipedia.org/wiki/Quadric

    Finding the rational points of a projective quadric amounts thus to solving a Diophantine equation. Given a rational point A over a quadric over a field F, the parametrization described in the preceding section provides rational points when the parameters are in F, and, conversely, every rational point of the quadric can be obtained from ...

  3. Singular point of a curve - Wikipedia

    en.wikipedia.org/wiki/Singular_point_of_a_curve

    Hence, it is technically more correct to discuss singular points of a smooth mapping here rather than a singular point of a curve. The above definitions can be extended to cover implicit curves which are defined as the zero set ⁠ ⁠ of a smooth function, and it is not necessary just to consider algebraic varieties. The definitions can be ...

  4. Algebraic curve - Wikipedia

    en.wikipedia.org/wiki/Algebraic_curve

    An algebraic curve in the Euclidean plane is the set of the points whose coordinates are the solutions of a bivariate polynomial equation p(x, y) = 0.This equation is often called the implicit equation of the curve, in contrast to the curves that are the graph of a function defining explicitly y as a function of x.

  5. Five points determine a conic - Wikipedia

    en.wikipedia.org/wiki/Five_points_determine_a_conic

    The two subtleties in the above analysis are that the resulting point is a quadratic equation (not a linear equation), and that the constraints are independent. The first is simple: if A , B , and C all vanish, then the equation D x + E y + F = 0 {\displaystyle Dx+Ey+F=0} defines a line, and any 3 points on this (indeed any number of points ...

  6. Quadric (algebraic geometry) - Wikipedia

    en.wikipedia.org/wiki/Quadric_(algebraic_geometry)

    The two families of lines on a smooth (split) quadric surface. In mathematics, a quadric or quadric hypersurface is the subspace of N-dimensional space defined by a polynomial equation of degree 2 over a field. Quadrics are fundamental examples in algebraic geometry. The theory is simplified by working in projective space rather than affine ...

  7. Cusp (singularity) - Wikipedia

    en.wikipedia.org/wiki/Cusp_(singularity)

    In mathematics, a cusp, sometimes called spinode in old texts, is a point on a curve where a moving point must reverse direction. A typical example is given in the figure. A cusp is thus a type of singular point of a curve. For a plane curve defined by an analytic, parametric equation

  8. Regular singular point - Wikipedia

    en.wikipedia.org/wiki/Regular_singular_point

    Then amongst singular points, an important distinction is made between a regular singular point, where the growth of solutions is bounded (in any small sector) by an algebraic function, and an irregular singular point, where the full solution set requires functions with higher growth rates.

  9. Adjunction formula - Wikipedia

    en.wikipedia.org/wiki/Adjunction_formula

    Then, the canonical sheaf is given by (,), which can be found using the decomposition of wedges of direct sums of vector bundles. Then, using the adjunction formula, a curve defined by the vanishing locus of a section f ∈ Γ ( O ( a , b ) ) {\displaystyle f\in \Gamma ({\mathcal {O}}(a,b))} , can be computed as