منابع مشابه
The Intersection Conics of Six Straight Lines
We investigate and visualize the manifold M of planes that intersect six straight lines of real projective three space in points of a conic section. It is dual to the apex-locus of the cones of second order that have six given tangents. In general M is algebraic of dimension two and class eight. It has 30 single and six double lines. We consider special cases, derive an algebraic equation of th...
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A geometric graph ( = gg) is a pair G = (V, E), where V is a finite set of points ( = vertices) in general position in the plane, and E is a set of open straight line segments ( = edges) whose endpoints are in V. G is a convex gg ( = egg) if V is the set of vertices of a convex polygon. For n 3 1, 0 se c (;) and m Z= 1 let 2 = Z(n ,e, m) (I, = I,(n, e, m)) be the maximal number such that for ev...
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Let $R$ be a commutative ring with identity and $M$ be an unitary $R$-module. The intersection graph of an $R$-module $M$, denoted by $Gamma(M)$, is a simple graph whose vertices are all non-trivial submodules of $M$ and two distinct vertices $N_1$ and $N_2$ are adjacent if and only if $N_1cap N_2neq 0$. In this article, we investigate the concept of a planar intersection graph and maximal subm...
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lines, pseudolines, polar coordinates, trilinear coordinates, non-linear programming, geometry We present a graph-drawing algorithm which respects extended co-linearity constraints. These are expressed as a set of ‘straight’ paths in a planar graph. Constraints of this sort are translated into a set of inequalities over polar coordinates of lines. These inequalities provide necessary and suffic...
متن کاملEuclid’s straight lines
We raise two questions on Euclid’s Elements: How to explain that Propositions 16 and 27 in his first book do not follow, strictly speaking, from his postulates (or are perhaps meaningless)? and: What are the mathematical consequences of the meanings of the term eutheia which we today often prefer to consider as different? The answer to the first question is that orientability is a tacit assumpt...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 2002
ISSN: 0012-365X
DOI: 10.1016/s0012-365x(02)00591-5