浅析平面内常见曲线定义及性质的应用

平面内常见曲线有:线段的垂直平分线,角平分线,圆及圆锥曲线等.他们的定义分别如下:(1)线段的垂直平分线是平面内到两定点的距离相等的点的轨迹.(2)角平分线是平面内到角两边距离相等的点的轨迹.(3)圆是平面内到一定点的距离等于定长的点的轨迹.     

对新课标选修教材中两个易错问题的辨析

问题1 平面内到定点F的距离比到定直线l的距离大(小)d的轨迹一定是以定点F为焦点的抛物线吗? 　　北师大版新课标教材<数学(选修2-1)>(以下简称新教材)第73页练习2第4题: 　　平面上动点M到点F(3,0)的距离比M到y轴的距离大3,求动点M满足的方程.……     

圆锥曲线的光学性质

抛物线绕其对称轴旋转形成的面称为抛物面,平行于抛物面旋转轴的平行光线束射入抛物面凹面镜时其反射光线聚集抛物线的焦点上。图1为抛物面凹面镜沿旋转轴的剖面图,抛物线上任意点P(x_0,y_0)的法线方程式为     

十年热考,题根研究——阿波罗尼斯圆

<正>上教版高二年级下学期数学练习册22页第4题:已知A,B两点相距10厘米,动点P到点A的距离是它到点B的距离的3倍,求点P的轨迹.公元前3世纪,古希腊数学家阿波罗尼斯(Apollonius)在?平面轨迹?一书中,曾研究了众多的平面轨迹问题,其中有如下结果:到两定点距离之比等于已知数的动点轨迹为直线或圆.     

Lorentz-Minkowski空间中旋转W超曲面

1841年,D elaunay获得如下定理:如果在一平面上沿定直线滚动一条二次圆锥直线,然后将其焦点的轨迹绕定直线旋转,则所得到的曲面具有常数平均曲率,反之,所有旋转常数平均曲率曲面(除球面外)都有如此构造.本文将以上的D elaunay定理推广到Lorentz-M inkow sk i空间Rn1 1中类空的Sm型旋转W超曲面.     

抓住轨迹意识，优化解题应用

<正>轨迹意识是平面解析几何中的一种重要行为意识,也是平面解析几何中的重要思想方法.除在解析几何中熟练应用外,在解三角形、平面向量以及立体几何等其他场合,也经常借助轨迹意识来解决相应的数学问题,直观形象.1 解析几何中的轨迹意识解析几何中的轨迹问题,其实质就是由曲线上的动点变化规律,按照一个条件的变化引起其他相关新动点的变化情况,利用对图形结构的理解、探索与联想,构建“形”与“数”之间的联系,进而探究新动点的轨迹.     

在创新思想指导下编制的一道解析几何开放题

椭圆、双曲线第一定义 :平面上到两个定点F1,F2 距离之和等于常数 ( >|F1F2 | )的动点的轨迹叫椭圆 ,两距离之差的绝对值等于常数 ( <|F1F2 | )的动点的轨迹叫双曲线 .圆锥曲线第二定义 :平面上到定点的距离与到定直线的距离的比等于常数e的动点的轨迹叫… ,换言之 :平面上到定点F的距离与定直线l的距离的e倍相等的点的轨迹叫… .在创新思想指导下 ,将第一、第二定义剪辑后再嫁接 ,提出开放的新问题 :若动点M到定点F的距离与M到定直线l的距离的e倍的和 (或差的绝对值 )等于常数 ,动点M的轨迹是什么呢 ?以定直线l为x轴 ,过定点F且与l垂…     

圆锥曲线统一定义的应用

椭圆、双曲线、抛物线统称为圆锥曲线.它们表示到定点F和定直线l的距离的比是一个常数e的点M的轨迹.当01时,点M的轨迹是双曲线;当e=1时,点M的轨迹是抛物线.其中定点F叫做焦点;定直线l叫做准线;定比e叫做离心率.这样的     

赏析和拓广2009年高考数学湖南卷第20题

题目在平面直角坐标系xOy中,点P到点F(3,0)的距离的4倍与它到直线x=2的距离的3倍之和记为d.当点P运动时,d恒等于点P的横坐标与18之和. 　　(Ⅰ)求点P的轨迹C; 　　(Ⅱ)设过点F的直线l与轨迹C相交于M,N两点,求线段MN长度的最大值.……     

一道易错题的解析

例题已知平面内有一定点A与一定直线l,点P是平面上的动点,且点P到l的距离比到点A的距离小2,则点P的轨迹是（）.（A）椭圆（B）双曲线（C）抛物线（D）无法确定许多同学都认为答案是（C）,因为大家习惯上都会像图1那样在平面内任取一点P,     

拓扑定理及其在超线性脉冲方程中的应用

本文研究一类含脉冲的非保守超线性方程的周期振动问题.通过详细刻画跳跃映射的角度函数,并应用相平面分析方法,本文证明方程的Poincaré映射有无穷多个不动点,而这些不动点对应了方程的无穷多个2π周期解.由于本文考虑的Poincaré映射不是同胚,所以,本文重新构造并证明了一个拓扑定理用于替代经典的Poincaré-Birkhoff扭转不动点定理.     

Director circles of conic sections

Given a conic section, the locus of a moving point in the plane of the conic section such that the two tangent lines drawn to the conic section from the moving point are all mutually perpendicular is a curve. In the case of an ellipse and hyperbola this curve is a circle referred to as the director circle. In the case of the parabola this curve coincides with the directrix of the parabola. The last section is devoted to the graphical illustrations of director circles for circles, parabolas, ellipses and hyperbolas using the built-in Maple V software of Scientific Work Place 3.0.     

A Nonholonomic Model of the Paul Trap

In this paper, equations of motion for the problem of a ball rolling without slipping on a rotating hyperbolic paraboloid are obtained. Integrals of motions and an invariant measure are found. A detailed linear stability analysis of the ball’s rotations at the saddle point of the hyperbolic paraboloid is made. A three-dimensional Poincaré map generated by the phase flow of the problem is numerically investigated and the existence of a region of bounded trajectories in a neighborhood of the saddle point of the paraboloid is demonstrated. It is shown that a similar problem of a ball rolling on a rotating paraboloid, considered within the framework of the rubber model, can be reduced to a Hamiltonian system which includes the Brower problem as a particular case.     

Topological properties of strongly monotone planar vector fields

We consider strongly monotone continuous planar vector fields with a finite number of fixed points. The fixed points fall into three classes, attractors, repellers and saddles. Naturally, the relative positions of the fixed points must obey a set of restrictions imposed by monotonicity. The study of these restrictions is the main goal of the paper. With any given vector field, we associate a matrix describing the arrangement of the fixed points on the plane. We then use these matrices to formulate simple necessary and sufficient conditions which allow one to determine whether a finite set of attractors, repellers and saddles at given positions on the plane can be realized as the fixed point set of a strongly monotone vector field.     

Computing minimum-area rectilinear convex hull and L-shape

We study the problems of computing two non-convex enclosing shapes with the minimum area; the L-shape and the rectilinear convex hull. Given a set of n points in the plane, we find an L-shape enclosing the points or a rectilinear convex hull of the point set with minimum area over all orientations. We show that the minimum enclosing shapes for fixed orientations change combinatorially at most O(n) times while rotating the coordinate system. Based on this, we propose efficient algorithms that compute both shapes with the minimum area over all orientations. The algorithms provide an efficient way of maintaining the set of extremal points, or the staircase, while rotating the coordinate system, and compute both minimum enclosing shapes in O(n²) time and O(n) space. We also show that the time complexity of maintaining the staircase can be improved if we use more space.     

General blow-ups of the projective plane

We study linear series on a projective plane blown up in a bunch of general points. Such series arise from plane curves of fixed degree with assigned fat base points. We give conditions (expressed as inequalities involving the number of points and the degree of the plane curves) on these series to be base point free, i.e. to define a morphism to a projective space. We also provide conditions for the morphism to be a higher order embedding. In the discussion of the optimality of obtained results we relate them to the Nagata Conjecture expressed in the language of Seshadri constants and we give a lower bound on these invariants.     

An orientation preserving fixed point free homeomorphism of the plane which admits no closed invariant line

Though fixed point free homeomorphisms of the plane would appear to exhibit the simplest dynamical behavior, we show that the minimal sets can be quite complex. Every homeomorphism which is conjugate to a translation must have a closed invariant line. However we construct an orientation preserving fixed point free homeomorphism of the plane which admits no closed invariant line. We verify that no such line exists by considering the ‘fundamental regions” of our example. Fundamental regions, studied first by Stephen Andrea, are equivalence classes of points in the plane associated with a given homeomorphism. Two points are said to be in the same equivalence class if they can be connected by an arc which diverges to infinity under both the forward and backward iterates of the homeomorphism. Our example contains no invariant fundamental regions.     

Linear Fractional Transformation Methods in $ {\shadC}^n $

We consider the generalization of linear fractional transformations of the plane to $ {\shadC}^n $ . Analogs of the one-variable theory are developed including fixed point sets and points of symmetry. The domains in $ {\shadC}^n $ that are images of the ball under these transformations are found. Finally, we see some examples where classical fixed point results follow from this theory in a natural way.     

Maxwell Strata and Cut Locus in the Sub-Riemannian Problem on the Engel Group

We consider the nilpotent left-invariant sub-Riemannian structure on the Engel group. This structure gives a fundamental local approximation of a generic rank 2 sub-Riemannian structure on a 4-manifold near a generic point (in particular, of the kinematic models of a car with a trailer). On the other hand, this is the simplest sub-Riemannian structure of step three. We describe the global structure of the cut locus (the set of points where geodesics lose their global optimality), the Maxwell set (the set of points that admit more than one minimizer), and the intersection of the cut locus with the caustic (the set of conjugate points along all geodesics). The group of symmetries of the cut locus is described: it is generated by a one-parameter group of dilations R₊ and a discrete group of reflections Z₂ × Z₂ × Z₂. The cut locus admits a stratification with 6 three-dimensional strata, 12 two-dimensional strata, and 2 one-dimensional strata. Three-dimensional strata of the cut locus are Maxwell strata of multiplicity 2 (for each point there are 2 minimizers). Two-dimensional strata of the cut locus consist of conjugate points. Finally, one-dimensional strata are Maxwell strata of infinite multiplicity, they consist of conjugate points as well. Projections of sub-Riemannian geodesics to the 2-dimensional plane of the distribution are Euler elasticae. For each point of the cut locus, we describe the Euler elasticae corresponding to minimizers coming to this point. Finally, we describe the structure of the optimal synthesis, i. e., the set of minimizers for each terminal point in the Engel group.     

二次曲线局部与整体的关系

用射影几何知识讨论欧氏平面上二次曲线局部与整体的关系,讨论如何通过二次曲线的一些已知点与切线判断它的类型,作出它的对称轴,渐近线,焦点与准线.