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  2. Paraboloid - Wikipedia

    en.wikipedia.org/wiki/Paraboloid

    The paraboloid is hyperbolic if every other plane section is either a hyperbola, or two crossing lines (in the case of a section by a tangent plane). The paraboloid is elliptic if every other nonempty plane section is either an ellipse, or a single point (in the case of a section by a tangent plane). A paraboloid is either elliptic or hyperbolic.

  3. Paraboloidal coordinates - Wikipedia

    en.wikipedia.org/wiki/Paraboloidal_coordinates

    Hence, the coordinates can be used to solve these equations in geometries with paraboloidal symmetry, i.e. with boundary conditions specified on sections of paraboloids. The Helmholtz equation is ( ∇ 2 + k 2 ) ψ = 0 {\displaystyle (\nabla ^{2}+k^{2})\psi =0} .

  4. Parabolic coordinates - Wikipedia

    en.wikipedia.org/wiki/Parabolic_coordinates

    The red paraboloid corresponds to τ=2, the blue paraboloid corresponds to σ=1, and the yellow half-plane corresponds to φ=-60°. The three surfaces intersect at the point P (shown as a black sphere) with Cartesian coordinates roughly (1.0, -1.732, 1.5).

  5. Ruled surface - Wikipedia

    en.wikipedia.org/wiki/Ruled_surface

    The hyperbolic paraboloid and the hyperboloid of one sheet are doubly ruled surfaces. The plane is the only surface which contains at least three distinct lines through each of its points (Fuchs & Tabachnikov 2007). The properties of being ruled or doubly ruled are preserved by projective maps, and therefore are concepts of projective geometry.

  6. Roman surface - Wikipedia

    en.wikipedia.org/wiki/Roman_surface

    Join the paraboloids y = xz and x = yz. The result is shown in Figure 1. Figure 1. The paraboloid y = x z is shown in blue and orange. The paraboloid x = y z is shown in cyan and purple. In the image the paraboloids are seen to intersect along the z = 0 axis. If the paraboloids are extended, they should also be seen to intersect along the lines ...

  7. Translation surface (differential geometry) - Wikipedia

    en.wikipedia.org/wiki/Translation_surface...

    If both curves are contained in a common plane, the translation surface is planar (part of a plane). This case is generally ignored. ellipt. paraboloid, parabol. cylinder, hyperbol. paraboloid as translation surface translation surface: the generating curves are a sine arc and a parabola arc Shifting a horizontal circle along a helix. Simple ...

  8. Euclidean planes in three-dimensional space - Wikipedia

    en.wikipedia.org/wiki/Euclidean_planes_in_three...

    This familiar equation for a plane is called the general form of the equation of the plane or just the plane equation. [6] Thus for example a regression equation of the form y = d + ax + cz (with b = −1) establishes a best-fit plane in three-dimensional space when there are two explanatory variables.

  9. Saddle point - Wikipedia

    en.wikipedia.org/wiki/Saddle_point

    A saddle point (in red) on the graph of z = x 2 − y 2 (hyperbolic paraboloid). In mathematics, a saddle point or minimax point [1] is a point on the surface of the graph of a function where the slopes (derivatives) in orthogonal directions are all zero (a critical point), but which is not a local extremum of the function. [2]