Complex.Acos Method Returns the angle that is the arc cosine of the specified complex number.
Imports System.Numerics
Module Example
Public Sub Main()
Dim values() As Complex = { New Complex(.5, 2),
New Complex(-.3, -.8) }
For Each value As Complex In values
Console.WriteLine(Complex.Cos(Complex.Acos(value)))
Next
End Sub
End Module