#### CharlieEuclid

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- Thread starter CharlieEuclid
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The question would be, in the proof you refer to, how is "congruence" proved? Euclid wouldn't explicitly use reflection in a proof, but if SAS applies, the proof could be valid. Can you give a reference for the statement you have in mind?

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Why are you posting this again, rather than responding to what was already said to you?

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Thanks for clearifying this. In view of this, the mathematician was right.

Thanks for your response. I'm new to this web site and after posting, I saw that a title to my question was required. I wrote a title and posted again. The reference you gave is excellent.

The question would be, in the proof you refer to, how is "congruence" proved? Euclid wouldn't explicitly use reflection in a proof, but if SAS applies, the proof could be valid. Can you give a reference for the statement you have in mind?

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The journal where I read that that particular proof of the Pythagorean theorem was not considerd correct by the mathematician was the bulletin of the american mathematical society. I will see if I can find the particular issue. The proof in question can be found in Issaics College Geometry text. I remember when I first saw this proof in a popular paper book on geometry. It struck me as much easier to understand than the usual proof by Euclid, but seemed less concise. For this reason I like not accepting reflection and inversion and to specify that side-angle-side, etc. should only apply to a certain class of triangles (this class can be mathematically specified).Thanks for clearifying this. In view of this, the mathematician was right.

Thanks for your response. I'm new to this web site and after posting, I saw that a title to my question was required. I wrote a title and posted again. The reference you gave is excellent.