Welcome to Math SE!
Have a look at how to format mathematics on Math SE.
Here is a very cool little tool called Detexify LaTeX where you can draw the symbol you are looking for and the system will tell you what the TeX command is.
Finally, I suggest that you bookmark this very useful MathJax tutorial
as a quick reference for future posts.
Using Wolfram, another useful tool is
TeXForm[expr] which converts a Wolfram input into TeX. It is possible to go from one language to the other with either
TeXForm[expr] to convert documents.
(See Generating and Importing TeX)