# Thread: Latex Code for One Set Minus Another ... ... A\B ... ...

1. Recently I posted the following text on the Analysis forum ...

" ... ... In order to demonstrate that $\displaystyle K$ is closed, we prove that $\displaystyle \mathbb{R}^n\K$ is open. Indeed, choose $\displaystyle y \notin K$ and define $\displaystyle O_j = \{ x \in \mathbb{R}^n \ \mid \ \mid \mid x - y \mid \mid \gt \frac{1}{j} \}$ for $\displaystyle j \in \mathbb{N}$. ... ... "

... and (as I did above) got a red \K in \mathbb{R}^n\K presumably because I'm misusing a special character \ in the code ...

What is wrong with what I've done and how do I correct it?

Further, how does one correctly write Latex code for one set minus another as in A\B?

Peter

2. This works, although there might be a better solution...

\mathbb{R}^n\text{\\}K

gives:

$\displaystyle \mathbb{R}^n\text{\\}K$

Originally Posted by MarkFL
This works, although there might be a better solution...

\mathbb{R}^n\text{\\}K

gives:

$\displaystyle \mathbb{R}^n\text{\\}K$

Thanks Mark ... but seems strange to me that two \s are required in text{ \\ } ... but then ... hey ... that's the rules of the code

Thanks again ...

Peter

4. Originally Posted by Peter
Thanks Mark ... but seems strange to me that two \s are required in text{ \\ } ... but then ... hey ... that's the rules of the code

Thanks again ...

Peter
Yeah, you have to escape the escape character to get a literal character.

You can also use:

\mathbb{R}^n\backslash K

or:

\mathbb{R}^n\setminus K (this one has more padding to the left and right of the slash)

5. I also want to point out that in the "MHB Widgets" block to the right of the editor is "Detexify" listed as the second entry in the list, and clicking that will popup a window into which you can draw a character you wish to use, and it will give you in most cases several options to try.

6. Originally Posted by MarkFL
\mathbb{R}^n\setminus K (this one has more padding to the left and right of the slash)
This is the correct solution.

Originally Posted by Peter
What is wrong with what I've done and how do I correct it?
The command \K is undefined. TeX commands usually consist of a backslash followed by letters.