It doesn't matter what units they use, the actual expression used by atan must be unitless, since they cancel out who cares. Inventor would assume degrees because the output of the function is degrees. If you want to change it to "mm" or "in" or "lengths of string", go ahead but I wouldn't waste time on it since it will not affect your result.
Regards
Stew
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Stew, AICP
Inventor Professional 2013, Autodesk Simulation Multiphysics 2013
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