There's an atn function, to calculate arctan's... but no inverse functions for the other two? Am I overlooking them somehow? I need them!

Google "VB asin" and you see how to code them yourself. Apparently they are not included in VB.

Thanks.  Those are a lot cleaner than the guess & test versions I came up with.

Function ArcSin(X As Double) As Double
    ArcSin = Atn(X / Sqr(-X * X + 1))
End Function

Function ArcCos(X As Double) As Double
    ArcCos = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
End Function

Private Sub Command1_Click()
    ' replace the 0.5 below with the degree (in radians) that
    ' you want to calculate its ArcSin or ArcCos value
    MsgBox "ArcSin(0.5) = " & ArcSin(0.5)
    MsgBox "ArcCos(0.5) = " & ArcCos(0.5)
End Sub