<math> <apply><forall/> <bvar><ci>y</ci></bvar> <bvar><ci type="function">f</ci></bvar> <condition> <apply><in/> <ci>y</ci> <apply><csymbol definitionURL="domain"><mtext>Domain</mtext></csymbol> <apply><inverse/><ci type="function">f</ci></apply> </apply> </apply> </condition> <apply><eq/> <apply><ci type="function">f</ci> <apply><apply><inverse/><ci type="function">f</ci></apply> <ci>y</ci> </apply> </apply> <ci>y</ci> </apply> </apply> </math>