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*Proposition:*
For all formulas `A` and `B`, the following holds:

~( A/\B)iff ~ A\/ ~B,~( A\/B)iff ~ A/\ ~B.

*Consequence:* For all formulas `A` and `B`, we have:

A\/Biff ~(~A/\ ~B).

*Disjunction can thus be defined by conjunction and negation.*

Author: Wolfgang Schreiner

Last Modification: October 6, 1999