线是没有厚度的直的一维图形。在几何形状中,一条线在两个方向上无限延伸。它被描述为任意两点之间的最短距离。 A线也可以理解为沿一个特定方向彼此连接的多个点,它们之间没有间隙。
线段是一条线的一部分,该线由两个不同的端点界定,并以尽可能短的距离包含端点之间线上的每个点。
写下点的坐标的规则,该点将两个给定点P(x 1 ,y 1 )和Q(x 2 ,y 2 )的连接在内部按给定比率m 1 :m 2进行划分
- 绘制连接给定点P和Q的线段
- 写下四肢的p和Q坐标
- 令R(x,y)为输入以内部比例m 1 :m 2除以PQ
- 对于R的x坐标,将x 2乘以m 1并将x 1乘以m 2并乘积。将总和除以m 1 + m 2
- 对于R的y坐标,将y 2乘以m 1并将y 1乘以m 2并乘积。将总和除以m 1 + m 2
公式的推导
设P(x 1 ,y 1 )和Q(x 2 ,y 2 )是坐标平面中给定线的两端,R(x,y)是该线上的点,该点将PQ按比例进行划分m 1 :m 2使得
PR / RQ = m 1 / m 2 …(1)
垂直于x轴并通过R的绘制线PM,QN和RL绘制一条平行于x轴的直线,以在S处遇到MP,在T处遇到NQ。
因此,从图中我们可以说,
SR = ML = OL – OM = x – x1 …(2)
RT = LN = ON – Ol = x2 – x …(3)
PS = MS – MP = LR – MP = y – y1 …(4)
TQ = NQ – NT = NQ – LR = y2 – y …(5)
现在∆ SPR类似于∆ TQR
SR / RT = PR / RQ
通过使用等式2、3和1,我们知道,
x – x1 / x2 – x = m1 / m2
m2x – m2x1 = m1x2 – m1x
m1x + m2x = m1x2 + m2x1
(m1 + m2)x = m1x2 + m2x1
x = (m1x2 + m2x1) / (m1 + m2)
现在∆ SPR类似于∆ TQR,
所以,
PS/TQ = PR/RQ
By using equation 4, 5, and 1, we know,
y – y1 / y2 – y = m1/m2
m2y – m2y1 = m1y2 – m1y
m1y + m2y = m1y2 + m2y1
(m1 + m2)y = m1y2 + m2y1
y = (m1y2 + m2y1)/(m1 + m2)
因此,R(x,y)的坐标为
基于公式的样本问题
问题1:计算点P的坐标,该点将连接A(-3,3)和B(2,-7)的线按比例2:3划分
解决方案:
Let (x, y) be th co-ordinates of the point P which divides the line joining A(-3, 3) and B(2, -7) in the ratio 2:3, then
Applying the formulae,
x = (m1x2 + m2x1) / (m1 + m2)
x = {2 x 2 + 3 x (-3)} / (2 + 3)
x = (4 – 9) / 5
x = -5 / 5
x = -1
y = (m1y2 + m2y1) / (m1 + m2)
y = {2 x (-7) + 3 x 3} / (2 + 3)
y = (-14 + 9) / 5
y = -5 / 5
y = -1
Hence the co-ordinates of point P are (-1, -1).
问题2:如果将连接点A(4,-5)和B(4,5)的线除以点P,使得AP / AB = 2/5,请找到P的坐标。
解决方案:
给定AP / AB = 2/5
5AP = 2AB = 2(AP + PB)
3AP = 2PB
AP/PB = 2/3
AP:PB = 2:3
Thus the point P divides the line segment joining the points A(4, -5) and B(4, 5) in the ratio 2:3 internally.
Hence the coordinates of P are,
Px = (2 x 4 + 3 x 4)/(2 + 3)
= (8 + 12)/5
= 20/5
= 4
Py = (2 x 5 + 3 x (-5))/(2 + 3)
= (10 – 15)/5
= -5/5
= -1
Coordinates of P are (4, -1).
问题3:点P(2,-5)以什么比例划分连接点A(-3,5)和B(4,-9)的线段。
解决方案:
令P(2,-5)以k:1的比例划分连接点A(-3,3)和B(4,-9)的线段,即AP:PB = k:1
Therefore, Coordinates of P are,
Px = (k.4 + 1.(-3)) / (k + 1)
Py = (k.(-9) + 1 x 5)/(k + 1)
But P is (2, -5) therefore,
(4k – 3) / (k + 1) = 2 and (-9k + 5) / (k + 1) = -5
Solving any of the two equation we get k = 5/2
Therefore, the required ratio is 5/2:1 i.e. 5:2(internally)