All rational numbers have the property that their square is not 2 == 2 not in {r... | Hacker News

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		gamegoblin on April 28, 2015 \| parent \| context \| favorite \| on: When is proof by contradiction necessary? `All rational numbers have the property that their square is not 2` == `2 not in {r^2 for r in rationals}` == `sqrt(2) not in {r for r in rationals}` == `sqrt(2) not in rationals` It seems to me that you handwaved away the entire proof in your first sentence, without really proving anything.

ikeboy on April 28, 2015 [–]

I did, although the statement I gave can be proven without contradiction. I gave a proof in a different reply.

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