Attempt to prove by contradiction without automatic raising of hypotheses
cts
This command enables to attempt a proof by contradiction, without automatic raising of
hypotheses.
If the current goal is G, it is then transformed into:
¬G ⇒ bfalse
The hypotheses, completed by ¬G, must be able to generate bfalse.
This command is identical to ct, except that the generated hypotheses are not automatically
raised.
Let us consider the following proof obligation:
Hypothesis ENS = {e1,e2,e3,e4,e5} & tt: ENS & uu: ENS & not(uu = tt) & uu: {e1,e2,e3,e4} => tt = e5 & uu = e5 => tt = e1 Goal not(e2 = e5)
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We attempt a proof by contradiction, given the form of the goal.
PRI> cts Starting Contradiction
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¬¬e2 = e5 is simplified in e2 = e5. The goal becomes:
Goal e2=e5 => bfalse
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