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Solid geometry

From Wikipedia, the free encyclopedia
(Redirected fromSolid figure)
Field of mathematics dealing with three-dimensional Euclidean spaces
Not to be confused withthe film of the same name.
"Solid object" redirects here; not to be confused withRigid object.
"Solid surface" redirects here. For the material, seeSolid surface material.
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Hyperboloid of one sheet

Solid geometry orstereometry is thegeometry ofthree-dimensionalEuclidean space (3D space).[1]Asolid figure is theregion of 3D space bounded by atwo-dimensionalclosed surface; for example, a solidball consists of asphere and itsinterior.

Solid geometry deals with themeasurements ofvolumes of various solids, includingpyramids,prisms (and otherpolyhedrons),cubes,cylinders,cones (andtruncated cones).[2]

History

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ThePythagoreans dealt with theregular solids, but the pyramid, prism, cone and cylinder were not studied until thePlatonists.Eudoxus established their measurement, proving the pyramid and cone to have one-third the volume of a prism and cylinder on the same base and of the same height. He was probably also the discoverer of a proof that the volume enclosed by a sphere is proportional to the cube of itsradius.[3]

Topics

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Basic topics in solid geometry and stereometry include:

Advanced topics include:

List of solid figures

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For a more complete list and organization, seeList of mathematical shapes.

Whereas asphere is the surface of aball, for other solid figures it is sometimes ambiguous whether the term refers to the surface of the figure or the volume enclosed therein, notably for acylinder.

Major types of shapes that either constitute or define a volume.
FigureDefinitionsImages
Parallelepiped
Rhombohedron
CuboidRectangular cuboid
PolyhedronFlatpolygonalfaces, straightedges and sharp corners orvertices
Small stellated dodecahedron

Toroidal polyhedron
Uniform polyhedronRegular polygons asfaces and isvertex-transitive (i.e., there is anisometry mapping any vertex onto any other)
(Regular)
Tetrahedron andCube

Unform
Snub dodecahedron
PyramidApolyhedron comprising ann-sidedpolygonalbase and a vertex pointsquare pyramid
PrismApolyhedron comprising ann-sidedpolygonalbase, a second base which is atranslated copy (rigidly moved without rotation) of the first, andn otherfaces (necessarily allparallelograms) joiningcorresponding sides of the two baseshexagonal prism
AntiprismApolyhedron comprising ann-sidedpolygonalbase, a second base translated and rotated.sides]] of the two basessquare antiprism
BipyramidApolyhedron comprising ann-sidedpolygonal center with two apexes.triangular bipyramid
TrapezohedronApolyhedron with 2n kite faces around an axis, with half offsetstetragonal trapezohedron
ConeTapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called theapex orvertex
A right circular cone and an oblique circular cone
CylinderStraight parallel sides and a circular or oval cross section
A solid elliptic cylinder

A right and an oblique circular cylinder
EllipsoidA surface that may be obtained from asphere by deforming it by means of directionalscalings, or more generally, of anaffine transformation
Examples of ellipsoids
x2a2+y2b2+z2c2=1:{\displaystyle {x^{2} \over a^{2}}+{y^{2} \over b^{2}}+{z^{2} \over c^{2}}=1:}
sphere (top, a=b=c=4),

spheroid (bottom left, a=b=5, c=3),
tri-axial ellipsoid (bottom right, a=4.5, b=6, c=3)]]

LemonAlens (or less than half of a circular arc) rotated about an axis passing through the endpoints of the lens (or arc)[6]
HyperboloidAsurface that is generated by rotating ahyperbola around one of itsprincipal axes

Techniques

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Various techniques and tools are used in solid geometry. Among them,analytic geometry andvector techniques have a major impact by allowing the systematic use oflinear equations andmatrix algebra, which are important for higher dimensions.

Applications

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A major application of solid geometry and stereometry is in3D computer graphics.

See also

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Notes

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  1. ^The Britannica Guide to Geometry, Britannica Educational Publishing, 2010, pp. 67–68.
  2. ^Kiselev 2008.
  3. ^Paraphrased and taken in part from the1911 Encyclopædia Britannica.
  4. ^Robertson, Stewart Alexander (1984).Polytopes and Symmetry. Cambridge University Press. p. 75.ISBN 9780521277396.
  5. ^Dupuis, Nathan Fellowes (1893).Elements of Synthetic Solid Geometry. Macmillan. p. 53. RetrievedDecember 1, 2018.
  6. ^Weisstein, Eric W."Lemon".WolframMathWorld. Retrieved2019-11-04.

References

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Authority control databases: NationalEdit this at Wikidata
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