David K Butler (Uni of Adel)
DavidKButler@mathstodon.xyz
<p>Lecturer at Maths Learning Centre, Uni Adelaide (my views here). Grad Dip Ed & PhD Finite Geom. Love maths and helping people learn. he/him <a href="https://mathstodon.xyz/tags/MTBoS" class="mention hashtag" rel="tag">#<span>MTBoS</span></a> <a href="https://mathstodon.xyz/tags/100factorial" class="mention hashtag" rel="tag">#<span>100factorial</span></a></p>
Posts
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Post #1421424
You may not be interested to know, but I will tell you anyway: The number one million and one is equal to one hundred and one times ninety-nine hundred and one.
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Post #1421423
I helped a student make sense of direct proof, proof by contradiction and proof by contrapositive today, and it was quite successful, so I want to share it with you. When you prove the statement “If A, then B” directly, your proof usually goes like this: Suppose A [insert arguments here] Therefore B. When you prove the statement “If A, then B” by contradiction, your proof usually goes like this: Suppose A. Suppose not B. [insert arguments here] C But already, not C. Contradiction! Therefore B....
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Post #1421422
@andrejbauer @soaproot It was a typo. I meant contradiction.
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Post #1421421
@andrejbauer @soaproot I don’t see why this is an issue.
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Post #1421420
“Everybody is so terribly sensitive about the things they know best.” - from The Phantom Tollbooth, by Norton Juster
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Post #1421418
@andrejbauer @soaproot I just don’t see why they’re distinct. If the statement “B” in my proof by contradiction happened to be “not B” then it would be the same as your refutation by contradiction. (In a land where not not B is B, and I have never lived in a land where it’s not.) And vice versa.
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Post #1421417
@andrejbauer @soaproot And I’m sorry that my PhD in pure maths did not provide me with the training you think it should have. Feel free not to explain it to me, I’m just a stranger on the internet as are you.