Quadrangle, complete
From Encyclopedia of Mathematics
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A collection of four points (lying in a plane), no three of which lie on the same line, and the six lines connecting these points (cf. Fig.).
Figure: q076010a
The points are called the vertices, and the lines are called the edges of the complete quadrangle. Edges that have no common vertex are called opposite; the points of intersection of the opposite edges are called diagonal points.
If and are the points of intersection of the line with the lines and , then the four points form a harmonic quadruple of points. The dual figure to a quadrangle is called a quadrilateral — a collection of four lines (in a plane), no three of which contain a common point.
Comments
References
[a1] | H.S.M. Coxeter, "Projective geometry" , Springer (1987) pp. 7; 95 |
[a2] | H.S.M. Coxeter, "Introduction to geometry" , Wiley (1963) |
[a3] | M. Berger, "Geometry" , 1–2 , Springer (1987) (Translated from French) |
How to Cite This Entry:
Quadrangle, complete. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Quadrangle,_complete&oldid=17067
Quadrangle, complete. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Quadrangle,_complete&oldid=17067
This article was adapted from an original article by P.S. ModenovA.S. Parkhomenko (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article