Example
x/y := such q: 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