特殊位置定坐标

• 作 者: 朱亚邦
• 出 处: 中学生数理化(七年级数学)(配合人教社教材)
• 发表日期: 2014年03期
• 关键词: 平面直角坐标系 角平分线 已知点 点对称 第三象限 第四象限

为使大家更深入地理解和掌握平面直角坐标系的内容,现介绍特殊位置上的点的坐标的求法.一、坐标轴上的点点在x轴上,其纵坐标为0;点在y轴上,其横坐标为0.例1已知点B(m+3,2m-1)在y轴上,求点B的坐标.解析:为点B(m+3,2m-1)在y轴上,所以点B的横坐标为0,即m+3=0.解得m=-3.故2m-1=2×(-3)-1=-7.所以点B的坐标为(0,-7).

In order to make people understand and grasp the content of Cartesian coordinate system in depth, we will introduce the method of finding the coordinates of a point in a special position.One point on the coordinate axis is on the x-axis and its ordinate is 0; on the y-axis , The abscissa is 0. Example 1 Known point B (m + 3,2m-1) on the y-axis, find the coordinates of point B. Analysis: Point B (m +3, 2m-1) in the y Therefore, the abscissa of point B is 0, that is, m + 3 = 0. Solve m = -3, so 2m-1 = 2 × (-3) -1 = -7. So the coordinate of point B is ( 0, -7).