两条直线的交点的解法。

兰州人

直线方程

y=kx+b

第一条直线方程

b1=y1-k1*x1

第二条直线方程

b2=y2-k2*x1

交点X，Y一定在第一条和第二条直线上

y=k1*x+b1

y=k2*x+b2

联解

x= (b2-b1)/(k1-k2)

y= k2x+b2

程序如下

Sub mLSs()
  Dim Aa(3) As Variant
  Aa(0) = Array(-10, 3)
  Aa(1) = Array(20, 50)
  Aa(2) = Array(14, 10)
  Aa(3) = Array(-20, 56)
 
  Dim pp(0 To 2) As Double, ppp(0 To 2) As Double

  Dim kkk As Double
  Kab = (Aa(1)(1) - Aa(0)(1)) / (Aa(1)(0) - Aa(0)(0))
  kkk = -1 / Kab
  k1 = (Aa(1)(1) - Aa(0)(1)) / (Aa(1)(0) - Aa(0)(0))
  k2 = (Aa(3)(1) - Aa(2)(1)) / (Aa(3)(0) - Aa(2)(0))
  b1 = Aa(1)(1) - k1 * Aa(1)(0)
  b2 = Aa(3)(1) - k2 * Aa(3)(0)
  x = (b2 - b1) / (k1 - k2)
  y = k2 * x + b2
  Debug.Print x, y
ii = 0
  For jj = 0 To 1
    pp(jj) = Aa(ii)(jj)
    ppp(jj) = Aa(ii + 1)(jj)
  Next jj
  Set ll = ThisDrawing.ModelSpace.AddLine(pp, ppp)
  ll.color = 1
 
ii = 2
  For jj = 0 To 1
    pp(jj) = Aa(ii)(jj)
    ppp(jj) = Aa(ii + 1)(jj)
  Next jj
  Set ll = ThisDrawing.ModelSpace.AddLine(pp, ppp)
  ll.color = 2

End Sub

带功能函数

'Vertical Point

Function VerticalPoint(lineVar As Variant, Delta As Double) As Variant
  Dim Kab, Kac
  Kab = (lineVar(1)(1) - lineVar(0)(1)) / (lineVar(1)(0) - lineVar(0)(0))
  Kac = -1 / Kab
  VerticalPoint = Array(lineVar(1)(0) + Delta / Sqr(1 + Kac ^ 2), lineVar(1)(1) - Delta / Sqr(1 + (1 / Kac) ^ 2), 0) 
End Function

'  Paralle Line
Function yParallelLine(linePoint As Variant, K As Double, Y As Double, Z As Double) 'As Variant
  Dim tempX As Double
  tempX = (Y - linePoint(1)) / K + linePoint(0)
  yParallelLine = Array(tempX, Y, Z)
End Function

' Slope in Xy Plane
Function xySlope(Point1 As Variant, Point2) As Double
  xySlope = (Point2(1) - Point1(1)) / (Point2(0) - Point1(0))
End Function