Post #2491870
2024-07-29 14:41 UTC
@DavidKButler@mathstodon.xyz Oooh nice. Also easily adapted to #constructiveMathematics as follows. The first and third work as you stated. The second one is the one which doesn't, but a modified variation of it does:
When you prove the statement “If A, then not B” by contradiction (what @andrejbauer@mathstodon.xyz calls "proof of negation"), your proof usually goes like this:
Suppose A.
Suppose B.
[insert arguments here]
C
But already, not C.
Contradiction!
Therefore not B.
Replies (1)
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@DavidKButler@mathstodon.xyz 2024-07-29 21:43
@soaproot@sfba.social @andrejbauer@mathstodon.xyz Interestingly I was talking to the student about what indicates contraction might be a good thing to try, and it’s often that the goal is stated as a negative to begin with.