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March 5

Does anyone know what this charcter is?

At s:Page:Cyclopaedia, Chambers - Volume 1.djvu/351, in the second column in the original text, in the second paragraph of the section on the equal sign (the one starting with This Character was firſt, the sixth paragraph to start from the top of the page) there is a weird symbol that looks like a backwards ∝. Does anyone know if this is represented in unicode? I can't find anything, but it must have been somewhat common, since the publisher of the book would have had to have it in print (the book was published in 1728). 🌺 Cremastra (talk) 21:57, 5 March 2024 (UTC)[reply]

This page describes mathematical notation used by Descartes: [1]. He introduced some notations that are standard today, but the backwards "∝" for equality is one that didn't catch on. I can't find it in Unicode or in any modern usage. Here's a book with more history on Descartes' equals sign and our modern one: [2]. --Amble (talk) 23:18, 5 March 2024 (UTC)[reply]

(Edit Conflict) The relevant paragraphs state '= is the Sign of Equality' ... 'Des Cartes in lieu of it uses ∝'.

Equals sign states:

"The symbol = was not immediately popular. The symbol || was used by some and æ (or œ), from the Latin word aequalis meaning equal, was widely used into the 1700s" (History of Mathematics, University of St Andrews).

So I suppose it might be a sloppily OCR-recognized æ or œ), unless someone would be a bigger expert on Descartes. 惑乱 Wakuran (talk) 23:23, 5 March 2024 (UTC)[reply]

I read the same paragraph in equals sign, and had the same thought, but OCR mistakes don't really make sense in an original text. I think I'll extract an image from it and insert it into the transcribed text for now. Thanks, 🌺 Cremastra (talk) 00:15, 6 March 2024 (UTC)[reply]

Or you could do this: ∝. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:39, 6 March 2024 (UTC)[reply]

Or this: ∝ ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:10, 6 March 2024 (UTC)[reply]

Ah, hadn't thought of that, thanks. 🌺 Cremastra (talk) 13:31, 6 March 2024 (UTC)[reply]

When books were manually typeset using movable type, the typesetter could insert a type piece turned upside down, rotated by 180°, or rotate it by just 90°, which explains why many

\infty

symbols in older printed books are not rotationally symmetric, like 8 : they are the figure 8 on its side. This can explain its use here if ∝ was available in type. --Lambiam 11:16, 6 March 2024 (UTC)[reply]

Florian Cajori's A History of Mathematical Notations says that Descartes "probably intended" his equality sign "to represent the first two letters in the [Latin] word aequalis" (so in effect it was meant as an ae-ligature like æ), but the symbol that was typeset was probably the sign for Taurus, rotated anticlockwise 90°.

By the way, the double horizontal line for an equals sign is usually credited to Robert Recorde.

--142.112.220.50 (talk) 18:28, 6 March 2024 (UTC)[reply]

Courtesy link: A History of Mathematical Notations#External links. 2A02:C7B:210:BA00:8458:F303:FDB1:5E14 (talk) 19:00, 6 March 2024 (UTC)[reply]

Amble already linked the book (and indeed the relevant passage) in the first response to this query, above. Deor (talk) 21:09, 6 March 2024 (UTC)[reply]

Thomas Harriot's symbol may have been substantially different from our present symbol,^[3] more like

\top \!\!\!\!\!\bot \!\!\top \!\!\!\!\!\bot .

More info (based on Cajori) can also be found in MacTutor's Earliest Uses of Symbols of Relation. Recorde may not have been the very first, and he used his paire of paralleles only in his 1557 book The Whetstone of Witte, in the lengthy, somewhat cumbersome form "=====". It is unclear when the use of our paire of paralleles of much shorter but of equally equalle lengthe became widespread. --Lambiam 22:53, 6 March 2024 (UTC)[reply]

There's a story that during WW2 someone adapted typewriters for various Asian languages, and in Burmese he got one of the letters upside-down. When he became aware of his error, he offered to correct it but was told, never mind, it is now an accepted variant. —Tamfang (talk) 19:49, 7 March 2024 (UTC)[reply]