Other Definitions
spheroid (dict)
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SpheroidA spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. If the ellipse is rotated about its major axis, the surface is called a prolate spheroid (similar to the shape of a rugby ball or cigar). If the minor axis is chosen, the surface is called an oblate spheroid (similar to the shape of the planet Earth). A spheroid can also be characterised as an ellipsoid having two equal semi-axes, as represented by the equation -
A prolate spheroid has one semiaxis longer than the other two, (a > b); an oblate spheroid has two equal semiaxes that are longer than the third one(a < b) and can resembles a disk. - Prolate spheroid.
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- Oblate spheroid.
| The sphere is a special case of the spheroid in which the generating ellipse is a circle. Volume Prolate spheroid: - volume is
Oblate spheroid: - volume is
where - a is the major axis length
- b is the minor axis length
Surface area A prolate spheroid has surface area -
An oblate spheroid has surface area - .
Here e is the eccentricity of the ellipse, defined as -
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