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x/y:=suchq:q*y=x.

- 12/4 = 3 because
*Existence:***exists**`q`:`q`*4 = 12 (because 3*4 = 12);*Unicity:***forall**`q`:`q`*4 = 12 =>`q`= 3

- We must
*not*assume that (1/0)*0 = 1, because we cannot prove**exists**`q`:`q`*0 = 1.

*Take care when reasoning about implicitly defined functions.*

Author: Wolfgang Schreiner

Last Modification: October 14, 1999