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对称问题是学生学习的难点。解析几何中的对称问题包括轴对称和中心对称两类。基本知识包括:1.中心对称:点关于点成中心对称的.对称中心恰是这两点为端点的线段的中点,因此中心对称的问题是线段中点坐标公式的应用问题。2.轴对称由轴对称定义知,对称轴即为两对称点连线的“垂直平分线”.利用“垂直”“平分”这两个条件建立方程组,就可求出对称点的坐标。【典型例题】【例1】求直线a:x+2y-4=0关于直线l:3x-y-1=0对称的直
Symmetry is the difficulty of students learning. Symmetry problems in analytical geometry include axial symmetry and centrosymmetry. The basic knowledge includes: 1. Center Symmetry: The point is symmetric about a point, and the center of symmetry is just the midpoint between the two end points. Therefore, the problem of center symmetry is the application of the formula of midpoint coordinates. 2. Axisymmetry is defined by the axis of symmetry, the symmetry axis is the line connecting two symmetry “Vertical bisector ” Use “Vertical ” “bisector ” These two conditions to establish equations, you can The coordinates of the point of symmetry. Typical example】 【Example 1 Find a straight line a: x + 2y-4 = 0 on the straight line l: 3x-y-1 = 0 Symmetrical straight