mathematical operator disappear

I have a problem with mathematical operators such as "=", "+" etc. Whenever I type them within a mathematical environment (equation, eqnarray, in line equations via $...$, displayed equation via $$...$$) they are not then displayed on the pdf version. I am using the packages:

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}


And if I type:

$$\mathbb{E}\left[f_{0}\left(t\right)\right] = 0$$


I don't get the signal "="

\documentclass[10pt,a4paper,twocolumn]{article}
\renewcommand{\familydefault}{\sfdefault}
\usepackage[english]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{fourier}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{csquotes}
\usepackage{multirow}
\usepackage{lxfonts}
\setcounter{secnumdepth}{1}

\begin{document}

$$\mathbb{E}\left[f_{0}\left(t\right)\right] = 0$$

\end{document}

• Please help us to help you and add a minimal working example (MWE) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with \documentclass{...} and ending with \end{document}. – jub0bs Nov 23 '14 at 15:45
• Please post a complete small document that has the problem, and show the log you get: we can not say much from an incomplete fragment – David Carlisle Nov 23 '14 at 15:45
• \documentclass[10pt,a4paper,twocolumn]{article} \renewcommand{\familydefault}{\sfdefault} \usepackage[english]{babel} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{fourier} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{csquotes} \usepackage{multirow} \usepackage{lxfonts} \setcounter{secnumdepth}{1} \begin{document} ... \mathbb{E}\left[f_{0}\left(t\right)\right] = 0 – Filippo Gatti Nov 23 '14 at 15:48
• Remove \usepackage{fourier} – egreg Nov 23 '14 at 15:51
• this problem with fourier has been reported before; one such question: < and > symbols don't appear using mathpazo and Memoir – barbara beeton Nov 23 '14 at 16:38

Never pile up font package loading. The fourier package uses math fonts with a different encoding from the standard, so it changes several slot positions.

On the other hand, the lxfonts use the standard encodings for math symbols, so loading fourier will have strange effects like the one you're describing.

By the way, your package loading order is a bit confused. And you definitely don't need \left and \right in that equation.

\documentclass[10pt,a4paper,twocolumn]{article}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\usepackage{lxfonts}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{csquotes}
\usepackage{multirow}% <--- do you really need it?

\renewcommand{\familydefault}{\sfdefault}
\setcounter{secnumdepth}{1}

\begin{document}

$$\mathbb{E}[f_{0}(t)] = 0$$

\end{document}


I'm not sure the result is really beautiful, though.

You might try the very recent newtxsf package:

\documentclass[10pt,a4paper,twocolumn]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\usepackage{newtxsf}

\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{csquotes}
\usepackage{multirow}% <--- do you really need it?

\renewcommand{\familydefault}{\sfdefault}
\setcounter{secnumdepth}{1}

\begin{document}

Some words before the equation so to see the
effect we get
$$\mathbb{E}[f_{0}(t)] = 0$$
And something after it.

\end{document}


• Talking about the loading order of packages, is there a preferable/correct order of loading babel, fontenc, and inputenc? – Svend Tveskæg Nov 23 '14 at 16:10
• @SvendTveskæg I usually have fontenc, inputenc and babel. Surely babel should go after inputenc in case non Latin alphabets are required; years ago, loading inputenc after fontenc might have strange effects in some cases (not reproducible any more, I believe). – egreg Nov 23 '14 at 16:14