Fundamental Groups of Triangle Geometries

利用Building理论获得一种计算某些三角几何的基本群的新的方法.这种方法能够容易地计算出无限多有限三角几何的基拓扑基本群.     

三角几何的基本群

利用Ｂｕｉｌｄｉｎｇ理论获得一种计算某些三角几何的基本群的新方法，这种方法能够容易地计算出无限多有限三角几何的基拓扑基本群。     

上三角Toeplitz矩阵的一个结论

本得出了上三角Toeplitz矩阵关于矩阵乘法构成一交换群的结果,并给出其逆矩阵的计算方法．     

上三角Toeplitz矩阵的一个结论

本文得出了上三角 Ｔｏｅｐｌｉｔｚ 矩阵关于矩阵乘法构成一交换群的结果,并给出其逆矩阵的计算方法．     

锐角的三角比在综合题解题中的应用

<正>锐角的三角比是三角函数概念的准备,是后续学习的基础．锐角的三角比也是中考中一个重要的考察点,但主要出现在实际问题背景下的数学问题中．在实际教学中我们发现,利用锐角的三角比去求解几何类综合题,可能比单纯的从几何角度思考解题更容易,有意想不到的良好效果．现通过一道综合题实例分别从几何角度和锐角的三角比角度进行方法介绍,具体如下．     

三角代换在竞赛中的应用

三角是中学数学的重要内容之一,其基础主要是几何中的相似形和圆．研究方法主要是代数变形和图象分析．因此,三角的研究已经初步把代数与几何联系起来了．本文讲讲三角代换在竞赛中的应用．     

例析解平面向量问题的常用方法与技巧

向量是近代数学最基本的概念之,它具有代数形式和几何形式的“双重身份”．是沟逋几何、代数、三角等内容的桥梁．“平面向量”足高中数学知识体系的重要组成部分,     

几何题的三角证法

利用三角法证几何题,是一种常用的方法。几何中有大量问题都可以用三角法加以解决。 用三角法证几何题,有以下优点: 1.几何法往往需要作比较巧妙的辅助线,而三角法在许多情况下,利用现有的图形,不需或少需辅助线,而且辅助线一般说来也比较明显,比较容易想,因而使图形比较简洁。 2.由于三角法是利用对含有三角函数的式子进行化简,计算,证明来进行证明,而这样的方法常常有成法可循,思路一般说来比几何法要简单些,容易被学生所理解、掌握。不单是思路,就是证明过程在     

三角型应用题选解

三角在几何、物理、测量、航海、天文等许多方面都有广泛的应用．对上述有关的一些应用题,我们经常把问题转化为三角问题,然后运用三角的知识和方法,将问题解决．     

例说三角解析几何试题的复数解法

例说三角解析几何试题的复数解法汪民岳（安徽省泾县中学２４２５００）复数沟通了代数、三角及几何之间联系．高考中有些三角、解析几何试题，应用复数知识去解，常常能获得明快，简捷解法．１应用复数运算的几何意义用三角试题１．１求三角函数值天。（１９９２年全国高...     

Projektive Darstellung der Moulton-Ebenen

The Moulton planes can be characterized as 2-dimensional topological projective planes having a 4-dimensional collineation group, which fixes exactly one nonincident point-line-pair aw. We give a representation of these geometries on the real protective plane such that a and W coincide with the origin and the line of infinity. This representation shows that the collineation groups of nonisomorphic Moulton planes act differently, although they are isomorphic as topological groups.     

A topological characterization of the Sierpiński triangle

We present a topological characterization of the Sierpiński triangle. This answers question 58 from the Problem book of the Open Problem Seminar held at Charles University. In fact we give a characterization of the Apollonian gasket first. Consequently we show that any subcontinuum of the Apollonian gasket, whose boundary consists of three points, is homeomorphic to the Sierpiński triangle.     

Topological projective geometries

A concept of topological projective geometry is defined, which in contrast to the definitions given in [Mi] and [SÖ] does not contain any dimensional restrictions. Besides elementary properties it is shown in this paper that these topological geometries always possess a coordinatization over a uniquely determined topological division ring if the dimension is finite.Dedicated to Prof. Dr. Hanfried Lenz on his 70^th birthday     

On Scattered Convex Geometries

A convex geometry is a closure space satisfying the anti-exchange axiom. For several types of algebraic convex geometries we describe when the collection of closed sets is order scattered, in terms of obstructions to the semilattice of compact elements. In particular, a semilattice Ω(η), that does not appear among minimal obstructions to order-scattered algebraic modular lattices, plays a prominent role in convex geometries case. The connection to topological scatteredness is established in convex geometries of relatively convex sets.     

The affine representation theorem for abstract convex geometries

A convex geometry is a combinatorial abstract model introduced by Edelman and Jamison which captures a combinatorial essence of “convexity” shared by some objects including finite point sets, partially ordered sets, trees, rooted graphs. In this paper, we introduce a generalized convex shelling, and show that every convex geometry can be represented as a generalized convex shelling. This is “the representation theorem for convex geometries” analogous to “the representation theorem for oriented matroids” by Folkman and Lawrence. An important feature is that our representation theorem is affine-geometric while that for oriented matroids is topological. Thus our representation theorem indicates the intrinsic simplicity of convex geometries, and opens a new research direction in the theory of convex geometries.     

A New Approach to Investigation of Carnot�CCarath��odory Geometry

We develop a new approach to studying the geometry of Carnot–Carathéodory spaces under minimal assumptions on the smoothness of basis vector fields. We obtain quantitative comparison estimates for the local geometries of two different local Carnot groups, as well as of a local Carnot group and the original space. As corollaries, we deduce some results that are well-known and basic for the “smooth” case: the generalized triangle inequality for d _∞, the local approximation theorem for the quasimetric d _∞, the Rashevskiǐ–Chow theorem, the ball-box theorem, and so on.     

Repeated Richardson extrapolation applied to the two-dimensional Laplace equation using triangular and square grids

The focus of this work is to verify the efficiency of the Repeated Richardson Extrapolation (RRE) to reduce the discretization error in a triangular grid and to compare the result to the one obtained for a square grid for the two-dimensional Laplace equation. Two different geometries were employed: the first one, a unitary square domain, was discretized into a square or triangular grid; and the second, a half square triangle, was discretized into a triangular grid. The methodology employed used the following conditions: the finite volume method, uniform grids, second-order accurate approximations, several variables of interest, Dirichlet boundary conditions, grids with up to 16,777,216 nodes for the square domain and up to 2097,152 nodes for the half square triangle domain, multigrid method, double precision, up to eleven Richardson extrapolations for the first domain and up to ten Richardson extrapolations for the second domain. It was verified that (1) RRE is efficient in reducing the discretization error in a triangular grid, achieving an effective order of approximately 11 for all the variables of interest for the first geometry; (2) for the same number of nodes and with or without RRE, the discretization error is smaller in a square grid than in a triangular grid; and (3) the magnitude of the numerical error reduction depends on, among other factors, the variable of interest and the domain geometry.     

Certain topological properties and duals of the domain of a triangle matrix in a sequence space

The matrix domain of the particular limitation methods Cesàro, Riesz, difference, summation and Euler were studied by several authors. In the present paper, certain topological properties and β- and γ-duals of the domain of a triangle matrix in a sequence space have been examined as an application of the characterization of the related matrix classes.