CAD tip # 12697:

If you need to show not only the main value of an angle but also a complementary opposite angle value (to 90°), you can use the following iLogic rule. It adds the "opposite" angle (in parentheses) to a selected, plain angular dimension. The displayed preecision will be the same as in the main dimension.

Any subsequent change of the angle or dimension style will not update the opposite angle dimension dynamically. You will need tu re-apply the rule. You can add an icon for this rule into Inventor ribbon e.g. by using our X-Tools (T4I).

The iLogic code:

'Adds opposite (90°) angle to ang.dimension (CAD Studio, 2020, www.cadforum.cz)
Dim oSelection As Object = ThisApplication.CommandManager.Pick(SelectionFilterEnum.kDrawingDimensionFilter, "Select an angular dimension:")
If IsNothing(oSelection) Then Return
If oSelection.Type <> kAngularGeneralDimensionObject Then
	MsgBox("This is not an angular dimension!", vbCritical, "Inventor")
	Return
End If
Dim oDim As AngularGeneralDimension = oSelection
Dim opposíte As Double = 90.0-oDim.ModelValue*180.0/PI 'opposite to 90°
If oDim.Text.FormattedText.Contains("°)") Then 'update
	oDim.Text.FormattedText = "<‍DimensionValue/>" & vbCrLf & "(" & CStr(Round(opposíte,oDim.Precision)) & "°)"
Else 'create
        oDim.Text.FormattedText = oDim.Text.FormattedText & vbCrLf & "(" & CStr(Round(opposíte,oDim.Precision)) & "°)"
End If
oDim.Text.HorizontalJustification = kAlignTextCenter