Visual basic matrices rotation - vb.net

Question

I made a square using 2 1 by 4 matrices, however now I want to rotate it by 45 degrees.
This is the code for the square (which works fine):
Dim m(1, 4) As Single
Dim n(1, 4) As Single
Dim formGraphics As System.Drawing.Graphics = Me.CreateGraphics()
Dim myPen As New System.Drawing.Pen(System.Drawing.Color.Black)
formGraphics.DrawLine(myPen, m(1, 1), m(1, 2), n(1, 4), n(1, 3))
formGraphics.DrawLine(myPen, n(1, 1), n(1, 3), m(1, 4), m(1, 3))
formGraphics.DrawLine(myPen, n(1, 2), n(1, 4), m(1, 2), m(1, 1))
formGraphics.DrawLine(myPen, n(1, 3), n(1, 3), m(1, 3), m(1, 1))
myPen.Dispose()
formGraphics.Dispose()
However when I try and turn it by 45 degrees I just cannot seem to get it right and I have no idea what I'm doing wrong or how to fix it. Code so far:
Dim b(1, 4) As Single
Dim c(1, 4) As Single
Dim A(2, 2) As Single
Dim radians As Double
Dim degrees As Double
degrees = 45
radians = degrees * ((2 * PI) / 360)
A(1, 1) = Cos(radians)
A(1, 2) = -Sin(radians)
A(2, 1) = Sin(radians)
A(2, 2) = Cos(radians)
c(1, 1) = (A(1, 1) * m(1, 2)) + (A(1, 2) * n(1, 2))
c(1, 2) = (A(1, 1) * m(1, 3)) + (A(2, 2) * n(1, 3))
c(1, 3) = (A(1, 1) * m(1, 3)) + (A(2, 2) * n(1, 3))
c(1, 4) = (A(1, 1) * m(1, 2)) + (A(1, 2) * n(1, 2))
b(1, 1) = (A(2, 1) * m(1, 2)) + (A(2, 2) * n(1, 2))
b(1, 2) = (A(2, 1) * m(1, 3)) + (A(2, 2) * n(1, 3))
b(1, 3) = (A(2, 1) * m(1, 3)) + (A(2, 2) * n(1, 3))
b(1, 4) = (A(2, 1) * m(1, 4)) + (A(2, 2) * n(1, 4))
Dim formGraphics As System.Drawing.Graphics = Me.CreateGraphics()
Dim myPen As New System.Drawing.Pen(System.Drawing.Color.Black)
formGraphics.DrawLine(myPen, b(1, 3), b(1, 4), c(1, 4), c(1, 4))
formGraphics.DrawLine(myPen, c(1, 4), c(1, 2), b(1, 4), b(1, 4))
formGraphics.DrawLine(myPen, b(1, 1), c(1, 2), b(1, 4), b(1, 4))
formGraphics.DrawLine(myPen, c(1, 4), c(1, 1), b(1, 4), b(1, 2))
myPen.Dispose()
formGraphics.Dispose()