How does one start learning Latex here?

I think there is a tutorial in MHF. Check out the first 2 threads : LaTex Help - Math Help Forum.

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Isaac
If the problem is too hard just let the Universe solve it.

Hi, I don't know if this is much help but I am just learning as I go. I.e.

whenever a question comes up in which I want to use a symbol, integral,

sum etc.. I just type into Google Latex (then the name of the symbol/

operator I am trying to get) and I seem to remember it in future.

Another tip : go in wikipedia and when you see a symbol you want to use in Latex, click on "edit" to edit the page. It will allow you to see the commands for the Latex images you are looking for. I learned a lot of Latex thanks to this.

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Isaac
If the problem is too hard just let the Universe solve it.

[LaTeX Error: Can't write to directory]
[LaTeX Error: Can't write to directory]

how does one check whether the expression is correct before actually posting?

Instead of clicking on "Submit Reply", click on the button next to it : "Preview Post".

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Isaac
If the problem is too hard just let the Universe solve it.

That's a great suggestion, and it certainly works, but you don't have to actually view the source for the entire page. Each equation image in Wikipedia has LaTeX alt text, so if you're using Firefox, one way to view the LaTeX is to right-click the equation and choose Properties. The alt text will show in the pop-up window.

In any browser though, if you just copy an equation and paste it into Notepad, you'll get the LaTeX for that equation. Two things important here. One, don't just right-click and choose "Copy Image". That won't do it. Best way to get it is to select it (drag the mouse over it) and use the shortcut (Ctrl+C or Command+C). Two, don't paste it into anything that recognizes an image (FrontPage, Word, PowerPoint, PhotoShop, etc.), because an image is what you get when you paste. If you paste it into a simple text editor such as Notepad or TextEdit, you'll get the LaTeX.

That's a much easier method than clicking on Edit if the page you're looking at is long and has lots of equations. The copy/paste method lets you get right to the one you want without looking at a lot of text & markup that you don't want.