Вычисление площади треугольника по координатам трех его вершин - VB

Option Explicit
Private Function pltrkoor(x1 As Single, y1 As Single, x2 As Single, y2 As Single, x3 As Single, y3 As Single) As Double
Dim a As Single, b As Single, c As Single, pp As Double
    a = rast(x1, y1, x2, y2)
    b = rast(x1, y1, x3, y3)
    c = rast(x3, y3, x2, y2)
    pp = (a + b + c) / 2
    pltrkoor = (pp * (pp - a) * (pp - b) * (pp - c)) ^ 0.5
End Function
Private Function rast(xn As Single, yn As Single, xk As Single, yk As Single) As Single
    rast = ((xk - xn) ^ 2 + (yk - yn) ^ 2) ^ 0.5
End Function
 
Private Sub Command1_Click()
Dim xa As Single, ya As Single
Dim xb As Single, yb As Single
Dim xc As Single, yc As Single
Dim s As Double
    Picture1.Cls
    xa = Val(Text1)
    ya = Val(Text2)
    xb = Val(Text3)
    yb = Val(Text4)
    xc = Val(Text5)
    yc = Val(Text6)
    s = pltrkoor(xa, ya, xb, yb, xc, yc)
    Picture1.Print Format(s, "0.00")
End Sub