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The following lines caught my attention while browsing source2e while looking for the definition of another command.



\def\@sqrt[#1]{\root #1\of}

What was \sqrtsign for? I tried \sqrtsign{x} and it outputs something similar to \sqrt{x}.

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up vote 7 down vote accepted

The definition of LaTeX's \sqrt is

\def\@sqrt[#1]{\root #1\of}

which means that if the optional argument is used (i.e., if the next character after \sqrt is [), \@sqrt is used (and this in its turn, uses \root#1\of whose definition can be found on page 210 of source2e.pdf) to typeset the radical index and the subradical expression; if no optional argument is given,\sqrtsign is used to typeset the subradical expression (\sqrtsign doesn't allow an optional argument).

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Thank whoever invented the find text and go to page capabilities of document readers:) – hpesoj626 Oct 3 '12 at 3:32

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