How to write integral in latex

Question

I'd like to write a formula like this in the above picture. But I got like this:

My code is: \int_{\Omega} f(\bold{x})\, \mathrm{d}\mathbf{x} =

1. Why the integral symbol looks rounded?
2. How to get the bolded "x" just like in the first picture?

Answer 1

The following code is a full example in which the integral takes the shape you want and the x is bold-font.

\documentclass{article}
\usepackage{bm}
\begin{document}
$
\displaystyle\int_{\Omega} f\left( \bm{x} \right) d\bm{x} =
$
\end{document}

I think your problem is that you have not included the integral inside the dollar symbols (which represent the mathematical mode). For the bold font I use the package bm, which provides the function \bm{...} for including bold-font text in mathematical mode.

Maybe other possibility is the compiler you are using. In my case, compiling it with pdfLaTeX, I have had no problem.

Answer 2

My welcome....in the community TeX.SE. For your question (I hope this time :-)) the answer is....

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}

\begin{document}
\[\int_{\Omega} f(\mathbf{x})\, \mathrm{d}\mathbf{x}\]
\end{document}

Previous answer: I think that your initial combination between Times New Roman (newtxtext - it is your clone) plus txfonts.

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}
\usepackage{newtxtext}
\usepackage{txfonts}
\begin{document}
\[\int_{\Omega} f(\mathbf{x})\, \mathrm{d}\mathbf{x}\]
\end{document}