Public Class Form1
    Dim pt() As Point = {New Point(140, 140), New Point(270, 5), New Point(270, _
      140)}
 
    Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        pt(1) = e.Location
        pt(2) = New Point(e.X, pt(0).Y)
        Me.Invalidate()
    End Sub
 
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        e.Graphics.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias
        Using fo As New Font("Arial", 12, FontStyle.Bold), sb As New SolidBrush( _
          Color.Red)
            e.Graphics.DrawPolygon(Pens.Blue, pt)
            e.Graphics.DrawString("a", fo, sb, pt(1).X - 8, -8 + pt(2).Y - (pt( _
              2).Y - pt(1).Y) \ 2)
            e.Graphics.DrawString("b", fo, sb, -5 + pt(0).X + (pt(2).X - pt( _
            0).X) \ 2, pt(0).Y - 10)
            e.Graphics.DrawString("c", fo, sb, -8 + pt(1).X - (pt(1).X - pt( _
            0).X) \ 2, -8 + pt(1).Y - +(pt(1).Y - pt(0).Y) \ 2)
        End Using
    End Sub
End Class