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Although the two outputs look quite similar, what is the advantage of using $f^\prime$ instead of $f'$? By the way, here is my code:

\[‎ ‎f^‎\prime ‎(x)=y‎ ‎\]‎
\[‎ ‎f'‎ ‎(x)=y‎ ‎\]‎‎
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There's no advantage in using $f^\prime$; it's just more awkward to type than $f'$ and the result is exactly the same. –  egreg Dec 15 '12 at 17:14

1 Answer 1

up vote 46 down vote accepted

' is defined in latex.ltx as active math character:

{\catcode`\'=\active \global\let'\active@math@prime}

The active ' looks for following ' and puts them together as superscript, a''' becomes a^{\prime\prime\prime}. Thus using ' makes the input easier to write.

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