VB 通过三个点画圆弧函数

Private Sub hyh(obj As Object, x1 As Single, y1 As Single, x2 As Single, y2 As Single, x3 As Single, y3 As Single)
    'obj：要画的窗体或控件
    Dim X As Single, Y As Single, r As Single
    obj.Cls
    obj.PSet (x1, y1)
    obj.PSet (x2, y2)
    obj.PSet (x3, y3)
    X = ((y3 - y1) * (y2 * y2 - y1 * y1 + x2 * x2 - x1 * x1) + (y2 - y1) * (y1 * y1 - y3 * y3 + x1 * x1 - x3 * x3)) / (2 * (x2 - x1) * (y3 - y1) - 2 * (x3 - x1) * (y2 - y1))
    Y = ((x3 - x1) * (x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1) + (x2 - x1) * (x1 * x1 - x3 * x3 + y1 * y1 - y3 * y3)) / (2 * (y2 - y1) * (x3 - x1) - 2 * (y3 - y1) * (x2 - x1))
    r = Sqr((x1 - X) * (x1 - X) + (y1 - Y) * (y1 - Y))
    obj.Circle (X, Y), r
End Sub