Possible Duplicate:

Define additional math operators to be typeset in roman

It may be a very simple question to people who know.

If I want to type commonly used functions like exponential function exp(x) or sinusoidal function sin(x), I use `\exp(x)`

and `\sin(x)`

in LaTeX and the results looks nice (fonts become different from other non-function characters). However, when I type error function `\erf(x)`

, it gives me error messages. If I remove `\`

, it compiles fine but the "erf(x)" fonts just look the same to other non-function characters. Could anyone please tell me how to make the error function fonts look like as exponential function in a math environment? Thanks very much.

## Best Answer

not every command imaginable are defined by default (assumes

`amsmath`

of course)