Portal:Mathematics
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There are approximately 23529 mathematics texts in Wikipedia.
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| 3D illustration of a stereographic projection from the north pole onto a plane below the sphere. |
In geometry, the stereographic projection is a particular mapping (function) that projects a sphere onto a plane. The projection is defined on the entire sphere, except at one point — the projection point. Where it is defined, the mapping is smooth and bijective. It is also conformal, meaning that it preserves angles. On the other hand, it does not preserve area, especially near the projection point.
Intuitively, then, the stereographic projection is a way of picturing the sphere as the plane, with some inevitable compromises. Because the sphere and the plane appear in many areas of mathematics and its applications, so does the stereographic projection; it finds use in diverse fields including differential geometry, complex analysis, cartography, geology, and crystallography.
| ...Archive | Image credit: Mark Howison | Read more... |
Picture of the month
Missing square puzzle animation.
The missing square puzzle is an optical illusion used in mathematics classes to help students reason about geometrical figures. It depicts two arrangements of shapes, each of which apparently forms a 13×5 right-angled triangle, but one of which has a 1×1 hole in it.
The puzzle works as the blue and red triangles are not similar so their hypotenuses are not parallel. In one arrangement the line bends one way, in one arrangement it bends the other way, and the gap between these bent lines is exactly one unit.
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Did you know...
- ...that some functions can be written as an infinite sum of trigonometric polynomials? This sum is called the Fourier series of that function.
- ...that outstanding mathematician Grigori Perelman was offered a Fields Medal in 2006, in part for his proof of the Poincaré conjecture, which he declined?
- ...that a regular heptagon is the regular polygon with the fewest number of sides which is not constructible with a compass and straightedge?
- ...that the Gudermannian function relates the regular trigonometric functions and the hyperbolic trigonometric functions without the use of complex numbers?
- ...that the Catalan numbers solve a number of problems in combinatorics such as the number of ways to completely parenthesize an algebraic expression with n+1 factors?
- ...that a ball can be cut up and reassembled into two balls the same size as the original (Banach-Tarski paradox)?
- ...that it is impossible to devise a single formula involving only polynomials and radicals for solving an arbitrary quintic equation?
- ...that Euler found 59 more amicable numbers while for 2000 years, only 3 pairs had been found before him?
- ...that you cannot knot strings in 4-dimensions? You can, however, knot 2-dimensional surfaces like spheres.
| Showing 9 items out of 26 | More did you know |
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Index of mathematics texts
| ARTICLE INDEX: | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0-9 |
| MATHEMATICIANS: | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
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