Option Explicit
Const pi = 3.14159265
Private Sub Command1_Click()
MsgBox arcsin(-1)
End Sub
Function arcsin(ByVal x As Single) As String
If Abs(x) > 1 Then
Exit Function
Else
If Abs(x) = 1 Then
arcsin = Sgn(x) * pi / 2
Else
arcsin = Atn(x / Sqr(1 - x * x))
End If
End If
arcsin = Format(arcsin * 180 / pi, "0.00") & "°"
End Function