Imports System.IO
Imports System.Drawing.Drawing2D
 
Public Class Form1
 
    Public seitea, seiteb, seitec As Double
    Public summe As Single
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        seitea = Val(TextBox1.Text)
        seiteb = Val(TextBox2.Text)
        seitec = Val(TextBox3.Text)
        Call dreieck(seitea, seiteb, seitec)
    End Sub
    Function dreieck(ByVal seitea As Double, ByVal seiteb As Double, ByVal _
      seitec As Double) As Double
        summe = (seitea + seiteb + seitec) / 2
        TextBox4.Text = Math.Round(summe, 3)
        Return seitea
    End Function
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        Dim g As Graphics = e.Graphics
        PictureBox1.BackColor = Color.Yellow
        g.DrawLine(Pens.Black, 100, 100, 200, 200)
        g.DrawLine(Pens.Black, summe, 100, 200, 200)
    End Sub
End Class