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## big cartesian product

Add tags LaTeX specific issues not fitting into one of the other forums of this category.

### big cartesian product

Hey everybody!
I want to illustrate a big cartesian product of sets. Is there a big version of the \times symbol for which indexes can be used? I don't want to use the \prod symbol, because in my math lectures we always use the cross symbol. Can somebody help me?
Hornisse
Hornisse

Posts: 4
Joined: Tue Oct 7th, 2008

### Re: big cartesian product

Hi Hornisse,

welcome to the board!
The ifsym package provides the symbols \Cross, \BigCross and \Smallcross, perhaps they would be useful for you.

Stefan

Stefan_K

Posts: 6901
Joined: Mon Mar 10th, 2008
Location: Hamburg, Germany

### Re: big cartesian product

Hey Stefan,
Thank you for your quick answer! Obviously I'm not an expert using LaTeX... Can you tell me how to download the ifsym package, respectively where I have to safe it? I tried it in the font folder, but it didn't work. The cross symbols you mentioned seem to be exactly what I need.
Hornisse
Hornisse

Posts: 4
Joined: Tue Oct 7th, 2008

### Re: big cartesian product

Hi Hornisse,

which LaTeX distribution do you use? Some distributions like MiKTeX and TeX Live offer a package management tool for the installation, so you don't need to install it manually.
Btw. now I'm away for some time and can give other answers in about 2 hours, but perhaps other users would provide additional help.

Stefan

Stefan_K

Posts: 6901
Joined: Mon Mar 10th, 2008
Location: Hamburg, Germany

### Re: big cartesian product

Hey!
I've just found out, that the package ifsym has already been installed. I checked it in the MikTex Package Manager. I also load the package in the pramble by \usepackage {ifsym}. Nevertheless the commands \Cross and \BigCross don't work.
Do you have any idea why?
Hornisse
Hornisse

Posts: 4
Joined: Tue Oct 7th, 2008

### Re: big cartesian product

Just set the geometry option according to the documentation:
Code: Select all  •  Open in writeLaTeX
\usepackage[geometry]{ifsym}

Stefan

Stefan_K

Posts: 6901
Joined: Mon Mar 10th, 2008
Location: Hamburg, Germany

### Re: big cartesian product

Hey!
At last I've been able to use the ifsym package. Unfortunately, as the symbols are geometric ones, I can't use them as mathematical ones, i.e. I can't add indexes exactly below und over the symbol. Any other ides where to get such a cross symbol? I thought that this should be a standard symbol... Crosses within a circle are actually used to indicate product-sigma-algebras. I definately need one without circle

Hornisse
Hornisse

Posts: 4
Joined: Tue Oct 7th, 2008

### Re: big cartesian product

Perhaps you will find an appropriate symbol in "The Comprehensive LaTeX Symbol List". It lists nearly 5000 symbols and may contain what you are searching for.

Best regards
Thorsten¹
LaTeX Community Moderator

¹ System: openSUSE 13.1 (Linux 3.11.10), TeX Live 2013 (vanilla), TeXworks 0.5 (r1351)
² Posting stopped indefinitely due to offenses

localghost
Site Moderator

Posts: 9219
Joined: Fri Feb 2nd, 2007
Location: Braunschweig, Germany

### Re: big cartesian product

This is my first post, so please forgive me if I don't follow standard conventions.

I don't like using symbols from other packages because they modify the standard AMS symbols.
An alternative is to define the command yourself and then use it as needed.

I use the standard \times command, and simply declare it to be a math-operator so that you can have the proper superscripts and subscripts.

Code: Select all  •  Open in writeLaTeX
\DeclareMathOperator*{\cart}{\times}Example 1: $X = \cart_{i\in I} X_i$\\Example 2: $X = \displaystyle\cart_{i\in I} X_i$\\Example 3:\begin{equation*}X = \cart_{i\in I} X_i\end{equation*}
brunosalcedo

Posts: 2
Joined: Sun Oct 30th, 2011