Definition of Vinculum
Date: 10/21/2004 at 15:49:43 From: Stephen Subject: the name of the bar used to indicate a repeating decimal What is the name (if it has one) of the bar placed over the set of repeated digits in a repeating decimal? Someone thought it was called a "vinculum", but the definition of vinculum is a horizontal bar that could be used in the same manner as grouping symbols (parentheses and such).
Date: 10/21/2004 at 23:25:22 From: Doctor Peterson Subject: Re: the name of the bar used to indicate a repeating decimal Hi, Stephen. I would call it a vinculum. The fact that it is being used in a slightly different way than the old usage for grouping does not mean it isn't the same symbol. (That usage for grouping, by the way, now exists mostly in radicals, _____ \/ 2+3 where the bar holds together the expression under it, and possibly as a fraction bar.) In decimals, the vinculum just indicates repetition in addition to grouping, and can still be called a vinculum. On the other hand, I have to admit that it is hard to find confirmation of that; dictionaries I have looked at refer the vinculum only to its use as a grouping symbol, and math history sources I have don't cover the origin of the repeating decimal usage or say what it is or was called. (I do, however, find historians using the word vinculum, as well as titulus, for the bar used over Roman numerals to multiply them by 1000, which is definitely more than just grouping.) Here is one source, which may or may not be authoritative enough: Vinculum http://mathworld.wolfram.com/Vinculum.html If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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