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Non-Convex Pentahedra

Published online by Cambridge University Press:  03 November 2016

M. Norgate
M. Norgate*
Affiliation:
Department of Museum Studies, University of Leicester, 152 Upper New Walk, Leicester
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Extract

Three straight lines are needed to enclose a finite region of a plane, a two-dimensional space. The polygon formed is a triangle. Different types of triangle are described by adjectives; scalene, isosceles, equilateral and acute angled, right angled, obtuse angled. All the triangles have a property in common: they are all convex.

Four lines form a quadrilateral. The convex examples are well known. There are two further types: those which are “re-entrant” having an interior angle greater than 180 degrees, a reflex angle; those in which a pair of opposite sides cross within the quadrilateral, a “crossed” quadrilateral.

Type
Research Article
Information
The Mathematical Gazette , Volume 54 , Issue 388 , May 1970 , pp. 115 - 124
Copyright
Copyright © Mathematical Association 1970

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References

Note on page No 119 * The symmetric difference of two sets, A⊕B, is the set of elements that are in either of the two sets but not in both.