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ellipsoid (Definition)

An ellipsoid is a subset of $ \mathbbmss{R}^3$ consisting of points $ (x,y,z)\in \mathbbmss{R}^3$ such that $$ \left(\frac{x}{a}\right)^2+ \left(\frac{y}{b}\right)^2+ \left(\frac{z}{c}\right)^2=1 $$ for some $a,b,c>0$ .

Properties

  1. If $a=b=c$ , the ellipsoid reduces to a sphere.
  2. If we fix the value of any of $x,y,z$ to some constant, say $x=C$ , we obtain an ellipse in the plane $(C,y,z)$ .
  3. The ellipse determined by $a,b,c$ is the unit sphere of the norm $$ \Vert v \Vert = v^T \operatorname{diag} (\frac{1}{a}, \frac{1}{b}, \frac{1}{c}) v, \quad v=(x,y,z)^T. $$




"ellipsoid" is owned by matte.
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See Also: sphere, quadratic surfaces, ellipse, volume of ellipsoid


Attachments:
spheroid (Definition) by rspuzio
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Cross-references: norm, unit sphere, plane, ellipse, fix, sphere, points, subset
There are 8 references to this entry.

This is version 3 of ellipsoid, born on 2005-01-12, modified 2005-02-19.
Object id is 6637, canonical name is Ellipsoid.
Accessed 4825 times total.

Classification:
AMS MSC51M05 (Geometry :: Real and complex geometry :: Euclidean geometries and generalizations)

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