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Bookmark or Share- Why does drawing $\\square$ mean the end of a proof?I had always used QED (quod erat demonstrandum) at the end of a proof until I was introduced to using Halmos' symbol. Since it was a 4-sided symbol, my mind has always associated this "quad" symbol with "quod".
- terminology - What is the meaning of the expression Q.E.D.? Is it ...Putting QED after that sentence was their way of saying, "and that's what I was trying to prove, so there, I've proved it". We aren't so strict about proofs anymore, but as a practical matter it's very useful to have a definitive mark that indicates the proof is over.
- What are the advantages of ending a proof with “QED”?As you know “QED” means “quod erat demonstrandum”, that is “what was to be shown”. It makes proofs more readable. Modern textbooks often conclude proofs with “which concludes the proof” or “which proves the assertion” or something. It’s the same thing, “QED” and the square are just convenient shorthands. $\endgroup$ –
- notation - Difference between $\square $ and $\blacksquare ...This Wikipedia page has an interesting discussion of the ways that QED has been translated into different languages (interestingly, not including English). I have seen other symbols used. This paper (which is famously the only PhD thesis in mathematics written by an NFL player) uses a white square with a vertical line going through it.
- Usage of the term Q.E.F. - Mathematics Stack ExchangeWhile researching the term Q.E.D last night, the phrase Q.E.F was mentioned, which was apparently "used by Euclid to indicate the end of the justification of a construction". Does Q.E.F indicate the
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