quadratic surfaces
The common equation of all quadratic surfaces is
where are constants and at least one of the six first does not vanish. The different non-degenerate kinds are as follows; we give also the simplest equation.
This classification is based on examining the signature (http://planetmath.org/SylvestersLaw) of the quadratic form
and the signature of the form
Note that, because of the fact that the equation describes the same surface if we simultaneously change the signs of all the coefficients, we obtain the same type of surface if we change all the signs in both signatures.
Surfaces without midpoints (http://planetmath.org/Midpoint3):
plotA.png
a) Elliptic paraboloid,
Signatures: , (or , )
Surfaces with one midpoint:
plotG
d) , ; it is a developable surface.
Signatures: , (or , )
Surfaces with infinitely many midpoints
b) Two intersecting planes,
Signatures: ,
d) Two parallel planes,
Signatures: , (or , )
e) Double plane,
Signatures: , (or , )
Algebraically, there are other possibilities for the signatures, such as and . However, these give rise to equations which have no real solutions, hence they have been ignored.
Title | quadratic surfaces |
Canonical name | QuadraticSurfaces |
Date of creation | 2013-03-22 14:59:40 |
Last modified on | 2013-03-22 14:59:40 |
Owner | pahio (2872) |
Last modified by | pahio (2872) |
Numerical id | 53 |
Author | pahio (2872) |
Entry type | Topic |
Classification | msc 51N20 |
Synonym | surfaces of second degree |
Related topic | TangentPlaneOfQuadraticSurface |
Related topic | Ellipsoid |
Related topic | SurfaceOfRevolution2 |
Related topic | GeneratricesOfOneSheetedHyperboloid |
Related topic | GeneratricesOfHyperbolicParaboloid |
Related topic | AnalyticGeometry |
Related topic | IntersectionOfQuadraticSurfaceAndPlane |
Defines | elliptic paraboloid |
Defines | hyperbolic paraboloid |
Defines | parabolic cylinder |
Defines | ellipsoid |
Defines | one-sheeted hyperboloid |
Defines | two-sheeted hyperboloid |
Defines | cone surface |
Defines | hyperbolic cylinder |
Defines | elliptic cylinder |