I want to search and replace the string

`sn`

by `\sn`

inside math equations.

I can't find how to do that, trying different options I get

undesired results.

Now more details:

I have written an article using the special function

`sn`

(Jacobi elliptic function). Example:

\[ \frac{sn^2(x)}{1+a sn(x)} \]

Afterwards I wanted to use the right typography for mathematical

functions and use the new command

`\sn`

.In the preamble I declared:

`\DeclareMathOperator{\sn}{sn}`

Then I wanted to replace every "sn" by "\sn". Example:

`\[ \frac{\sn^2(x)}{1+a \sn(x)} \]`

.I'm not able to do this in any way.

Thanks a lot.

Soszoe