Option Explicit

Private Sub Command1_Click()
GetSides
End Sub

Private Sub GetSides()
Dim dblSideA As Double
Dim dblSideB As Double
Dim dblSideC As Double

Dim dblAlpha As Double
Dim dblBetta As Double
Dim dblGamma As Double

Dim dblRadius As Double

On Error GoTo MethodExit

dblAlpha = CDbl(txtAlpha.Text)
dblBetta = CDbl(txtBetta.Text)
dblGamma = 180 - dblAlpha - dblBetta

If dblAlpha + dblBetta + dblGamma <> 180# Then
Err.Raise vbObjectError + 1000, , "Wrong angles"
End If

dblRadius = CDbl(txtRadius.Text)
dblSideB = GetSideB(dblRadius, dblAlpha, dblBetta)
dblSideC = GetSideC(dblRadius, dblAlpha, dblGamma)
dblSideA = GetSideA(dblRadius, dblAlpha, dblGamma)

MsgBox "Side A " & CStr(dblSideA)
MsgBox "Side B " & CStr(dblSideB)
MsgBox "Side C " & CStr(dblSideC)

MethodExit:
If Err.Number <> 0 Then
MsgBox "Error " & CStr(Err.Number) & " in GetSides" & vbCr & Err.Description
End If
End Sub

Private Function GetSideA(ByVal pdblC As Double, ByVal pdblAlpha As Double, ByVal pdblGamma As Double) As Double

On Error GoTo MethodExit

pdblGamma = GetRadians(pdblGamma)
pdblAlpha = GetRadians(pdblAlpha)

GetSideA = pdblC * (Sin(pdblAlpha) / Sin(pdblGamma))

MethodExit:
If Err.Number <> 0 Then
MsgBox "Error " & CStr(Err.Number) & " in GetSideA" & vbCr & Err.Description
End If

End Function

Private Function GetSideB(ByVal pdblRadius As Double, ByVal pdblAlpha As Double, ByVal pdblBetta As Double) As Double

On Error GoTo MethodExit

pdblBetta = GetRadians(pdblBetta)
pdblAlpha = GetRadians(pdblAlpha)

GetSideB = 2 * pdblRadius * (Sin(pdblBetta) / (Sin(pdblAlpha) * Sin(pdblAlpha)))

MethodExit:
If Err.Number <> 0 Then
MsgBox "Error " & CStr(Err.Number) & " in GetSideB" & vbCr & Err.Description
End If

End Function

Private Function GetSideC(ByVal pdblRadius As Double, ByVal pdblAlpha As Double, ByVal pdblGamma As Double) As Double

On Error GoTo MethodExit

pdblGamma = GetRadians(pdblGamma)
pdblAlpha = GetRadians(pdblAlpha)

GetSideC = 2 * pdblRadius * (Sin(pdblGamma) / (Sin(pdblAlpha) * Sin(pdblAlpha)))

MethodExit:
If Err.Number <> 0 Then
MsgBox "Error " & CStr(Err.Number) & " in GetSideC" & vbCr & Err.Description
End If

End Function

Private Function GetRadians(ByVal pdblDegrees As Double) As Double

On Error GoTo MethodExit

GetRadians = 3.14159265358979 * pdblDegrees / 180#

MethodExit:
If Err.Number <> 0 Then
MsgBox "Error " & CStr(Err.Number) & " in GetRadians" & vbCr & Err.Description
End If
End Function

Примечание: тестирование и возможная доводка предоставляю спрашивающему.

VladConn