Определить углы треугольника, длины сторон которого заданы - VB

Option Strict On
Option Explicit On
Imports System.Math
 
Public Class Form1
 
    'Функция ввода сторон треугольника
    Function vvod(ByVal T As TextBox) As Double
        Return CDbl(T.Text)
    End Function
 
    'Процедура вывода результата в TextBox
    Sub vivod(ByVal Z As Double, ByVal T As TextBox)
        T.Text = CStr(Z)
    End Sub
 
    'Функция вычисления полупериметра
    Public Function Полупериметр(ByVal a As Double, ByVal b As Double, ByVal c As Double) As Double
        Return CDbl((a + b + c) / 2)
    End Function
 
    'Функция вычисления тангенса половинного угла
    Sub тангенс(ByVal a As Double, ByVal b As Double, ByVal c As Double)
        Dim x As Double, y As Double, z As Double, p As Double
        p = Полупериметр(a, b, c)
        x = Sqrt((p - a) * (p - b) / p * (p - c))
        y = Sqrt((p - a) * (p - c) / p * (p - b))
        z = Sqrt((p - b) * (p - c) / p * (p - a))

    End Sub

    'Функция вычисления углов
    Sub углы(ByVal x As Double, ByVal y As Double, ByVal z As Double)
        Dim m, n, l As Double
        m = (Atan(x) * 2) * (180 / PI)
        n = (Atan(y) * 2) * (180 / PI)
        l = (Atan(z) * 2) * (180 / PI)
 
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        End
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim a As Double, b As Double, c As Double
        Dim m As Double, n As Double, l As Double
        a = vvod(TextBox1) : b = vvod(TextBox2) : c = vvod(TextBox3)
        vivod(CSng(m), TextBox4) : vivod(CSng(n), TextBox5) : vivod(CSng(l), TextBox6)

    End Sub
End Class