只要知道两个端点的坐标值,想找它们的连接线段的中点是非常容易的。最常见的做法就是使用中点公式来解。但是如果线段是水平或垂直的,也有其他方法解出中点。想知道如何快速解出中点坐标值,下面教你。
步骤
方法 1 的 2:
使用中点方程
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1
理解中点含义。中点就是线段中,离两端点距离相等的点。因此就是两个端点的平均,其坐标即横坐标和纵坐标的平均值。
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2
中点方程。中点方程就是把俩端点的横坐标的和以及纵坐标的和除以2,得到横坐标和纵坐标的平均值。[1]
这就是方程: [(x1 + x2)/2,( y1 + y2)/2]
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3
确定端点的坐标。如果不知道俩端点的坐标,是不能用上述公式的。本例中想要找出中点O的坐标(M (5,4)和 N (3,-4)的中点),即得到 (x1, y1) = (5, 4) , (x2, y2) = (3, -4)
- 注意每一对坐标都可以是 (x1, y1) 或 (x2, y2) 。因为你只是做加法,并且除以二求平均值,所以次序不重要。
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4
把对应系数代入方程。现在知道了端点坐标,代入公式即可,得到:
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5
解出中点。把适当系数代入以后,你只需要做个简单的计算,即可得到线段的中点值。即:
- [(5 + 3)/2, (4 + -4)/2] =
- [(8/2), (0/2)] =
- (4, 0)
- 端点 (5,4)、 (3, -4) 的中点是 (4,0)。
方法 2 的 2:
找出竖直线段或水平线段的中点
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1
找条竖直线或水平线。使用这个方法以前,需要知道如何找出竖直或水平线。下面是方法:[2]
- 如果一条线两端点的纵坐标相同,比如 (-3, 4) (5, 4),这条线段就是水平线段。
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- 如果一条线段两端点的横坐标相同,如 (2, 0) 、 (2, 3) ,则这条线段就是竖直线段。
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2
找出线段长度。对于水平线,你只要看看水平方向它的长度如何,对于竖直线,只要看看竖直方向长度如何。下面是方法:
- 水平线段俩端点为 (-3, 4) 、 (5, 4),长度为8。可以把横坐标的绝对值相加,来计算水平方向的长度: |-3| + |5| = 8
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- 竖直线段俩端点为 (2, 0) 、 (2, 3),长度为3,你可以把俩纵坐标绝对值相加,得到竖直方向长度: |0| + |3| = 3
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3
把线段长度除以2。知道了线段长度,除以2即可。
- 8/2 = 4
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- 3/2 = 1.5
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4
从某个端点算起距离上述长度的点。这步是最后一步,下面是具体方法:
- 要找出 (-3, 4) 、 (5, 4)的中点坐标,你只要从一边端点算起,往另一个端点方向数4个单位。 (-3, 4) 移动4个单位是 (1, 4) ,这里你不需要改变纵坐标了,因为两者都在一个水平线上。 (-3, 4)、 (5, 4) 中点坐标为 (1, 4)。
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- 要找出(2, 0) 、 (2, 3) 的中点,就从上或从下端数起1.5单位,得到中点。 (2, 0) 移动1.5单位是(2, 1.5) 。这里不需要改变横坐标的值,因为俩点都在一条竖线上。 (2, 0)、 (2, 3) 的中点是(2, 1.5)。
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你需要准备