It is possible to explain me the 18th proof of the irrationality of square root of 2 from the following site? http://www.cut-the-knot.org/proofs/sq_root.shtml
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$\begingroup$ The proof looks perfectly clear to me, except for a typo; CG=CD should be CG=GD (which is correctly stated earlier). What needs explanation? (This doesn't seem appropriate for MathOverflow.) $\endgroup$– Andreas BlassCommented Jun 26, 2010 at 17:31
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$\begingroup$ Closed, please check the FAQ. $\endgroup$– Kim MorrisonCommented Jun 26, 2010 at 18:24
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$\begingroup$ Christian: on a side note, you may like the analogous elementary proof of the irrationality of the other classic number, the golden ratio. Since it verifies the relation x=1+1/x and 1<x<2, if x were rational, x=p/q with 0<q<p, then also x=q/(p-q), and 0<p-q<q so there is no minimal denominator, a contradiction. $\endgroup$– Pietro MajerCommented Jun 26, 2010 at 18:33
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4$\begingroup$ -1 for not saying what the questioner doesn't understand... $\endgroup$– Yemon ChoiCommented Jun 26, 2010 at 19:37
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$\begingroup$ In the future, you'd have better luck directing such questions to sites like artofproblemsolving.com. $\endgroup$– Qiaochu YuanCommented Jun 26, 2010 at 22:09
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