VB求三角形外接圆心与半径

VB求三角形外接圆心与半径 day158

[求助] 求三角形外接圆心的位置坐标与半径长算法 己经：三个点  A（xa,ya),  B(xb,yb),  C(xc,yc)； 求：三点组成的三角形的外接圆心的坐标及半径长 写这种算法vb代码， 多谢！大侠！

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Option Explicit Private Sub Command1_Click() Dim xa As Single, xb As Single, xc As Single Dim ya As Single, yb As Single, yc As Single Dim x As Single, y As Single, r As Single Dim a11 As Single, a12 As Single, b1 As Single, a21 As Single, a22 As Single, b2 As Single Dim D As Single, D1 As Single, D2 As Single xa = InputBox("输入圆周坐标 xa") xb = InputBox("输入圆周坐标 xb") xc = InputBox("输入圆周坐标 xc") ya = InputBox("输入圆周坐标 ya") yb = InputBox("输入圆周坐标 yb") yc = InputBox("输入圆周坐标 yc") Print "坐标 xa, xb, xc = " & xa & ", " & xb & ", " & xc Print "坐标 ya, yb, yc = " & ya & ", " & yb & ", " & yc '推导： '(x - xa) ^ 2 + (y - ya) ^ 2 = (x - xb) ^ 2 + (y - yb) ^ 2   圆心到A点距离等于到B点距离 '(x - xa) ^ 2 + (y - ya) ^ 2 = (x - xc) ^ 2 + (y - yc) ^ 2   圆心到A点距离等于到C点距离 '(-2 * xa + 2 * xb) * x + (-2 * ya + 2 * yb) * y = -xa * xa + xb * xb - ya * ya + yb * yb '(-2 * xa + 2 * xc) * x + (-2 * ya + 2 * yc) * y = -xa * xa + xc * xc - ya * ya + yc * yc 'vvbb 答疑网 www.dayi.net a11 = -2 * xa + 2 * xb a12 = -2 * ya + 2 * yb b1 = -xa * xa + xb * xb - ya * ya + yb * yb a21 = -2 * xa + 2 * xc a22 = -2 * ya + 2 * yc b2 = -xa * xa + xc * xc - ya * ya + yc * yc D = a11 * a22 - a12 * a21 If D = 0 Then Print "系数行列式 D = 0，无解或无穷多解！" Exit Sub End If D1 = b1 * a22 - a12 * b2 D2 = a11 * b2 - b1 * a21 x = D1 / D y = D2 / D r = ((x - xa) ^ 2 + (y - ya) ^ 2) ^ 0.5 Print "圆心坐标 x, y = " & x & ", " & y, "半径 r = " & r End Sub ｆｒｏｍ：http://www.dayi.net/CExcellent/39392.asp