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[tlaplus] simple toy theorem
Let's say we have this simple theorem
THEOREM T ==
NEW NEW S(_), NEW U(_), NEW M(_), NEW P(_),
\A x : M(x) = S(x) /\ ~U(x),
\A x : P(x) = M(x)
\A x : P(x) => S(x)
It is true.
If I negate the goal to \E x : ~(P(x) => S(x)) same as \E x : P(x) /\ ~S(x) it becomes red.
However, if I add another assumption
NEW B(_), \A x : B(x) = S(x) /\ U(x),
The theorem turns green! How can this new assumption make the theorem true?
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