Helpful hint: In MathJax, use
\ln or \log or \lg for upright $\ln$, $\log$ and $\lg$, since these functions require non-italic typeface. Works with some other functions like \sin, too. The workaround for nonsupported functions is \mathrm{function}. — Jan 1 hour ago
I apparently can't see the difference in a compilation (pdflatex) between \mathrm and \operatorname. So, as in the title the question is: is there a difference? Which one is preferable in what occasions?
