Wikipedia:Reference desk/Archives/Mathematics/2016 November 29

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November 29

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Construction of higher roots of two

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Can   or   be constructed? יהודה שמחה ולדמן (talk) 17:28, 29 November 2016 (UTC)[reply]

You can always construct the geometric mean of two given lengths. Which means that if you are given a unit interval, you can construct the square root of any given number. This means you can construct   and in general  . But I believe you can't construct any other roots of 2. For example,   is famously non-constructible, so   can't be constructed either. -- Meni Rosenfeld (talk) 18:11, 29 November 2016 (UTC)[reply]
So how do we construct   as height in the right triangle with hypotenuse   ? יהודה שמחה ולדמן (talk) 18:54, 29 November 2016 (UTC)[reply]
You can see the details of the construction at http://math.stackexchange.com/a/708/153429. -- Meni Rosenfeld (talk) 19:35, 29 November 2016 (UTC)[reply]

"Equivalent to" vs "Approximately" symbols

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What is the difference between these symbols: ≍ ≈ ? I've seen "≈" used many times before (i.e. Pi ≈ 3.14). But "≍" is new to me. It seems they have a similar meaning? --209.203.125.162 (talk) 21:06, 29 November 2016 (UTC)[reply]

The ≍ symbol is sometimes used to denote equivalent "order of magnitude" in asymptotic analysis, for example, in Asymptotic notations. --Mark viking (talk) 21:49, 29 November 2016 (UTC)[reply]