How to type an infinity symbol in latex

Jarrao wrote:So the minimal example means that you not only enter the one line of code but also the necessary packages, etc., right? [...]

This question alone shows that you either did not follow the link or did not read the instructions provided, or only partially read them. Both are very rude. Links with further information contained in articles are to be understood as an integral part of answers. And yes, beginners can do that too. And the time you take for a proper example is more than worth it in terms of the answers to be expected.

You should also mark the source code as such in order to increase the readability of a post. The note about this is more than clearly visible when you write a post.

With the poor information so far, an answer is unfortunately not possible at the moment. Your question doesn't seem to be too important to you if you have to coax the information out of you individually and therefore have to invest additional time. Maybe we'll get on with your next attempt.

TeX and LaTeX, questions and answers - TeXwelt

¹ I'm sorry. My answers are limited. You have to ask the right questions.
² System: openSUSE 13.1 (Linux 3.11.6), TeX Live 2013, TeXworks 0.5 (r1349)
³ Currently learning TeX (and trying to understand).