Here is a Console application that should answer some of your questions:
Dim ang, radian As Double, deg As String
Dim Degrees As Double = Math.PI / 180
Console.WriteLine("Trigonometric functions use radians rather than degrees.")
Console.Write("Enter an angle in degrees: ")
deg = Console.ReadLine()
Double.TryParse(deg, ang)
If ang > 360 Then ang = 360
radian = ang * Degrees
Console.WriteLine(vbCrLf & "The sine of your angle is {0}", Math.Sin(radian))
Console.WriteLine("The cosine of your angle is {0}", Math.Cos(radian))
Console.WriteLine("The tangent of your angle is {0}", Math.Tan(radian))
Console.ReadLine()