Заданы координаты 3-х вершин треугольника (x1,y1) (x2, y2) (x3, y3). Отыскать

Sub PS()
    Dim x1 As Double, y1 As Double, x2 As Double, y2 As Double
    Dim x3 As Double, y3 As Double
    x1 = Cells(2, 2): y1 = Cells(2, 3)
    x2 = Cells(3, 2): y2 = Cells(3, 3)
    x3 = Cells(4, 2): y3 = Cells(4, 3)
    a = L(x1, y1, x2, y2)
    b = L(x2, y2, x3, y3)
    c = L(x3, y3, x1, y1)
    P = a + b + c
    Cells(6, 2) = P
    p2 = P / 2
    S = Sqr(p2 * (P - a) * (P - b) * (P - c))
    Cells(7, 2) = S
End Sub

Function L(x1 As Double, y1 As Double, x2 As Double, y2 As Double) As Double
    L = Sqr((x2 - x1) ^ 2 + (y2 - y1) ^ 2)
End Function