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I was curious (even though this is a very amateur question)... what would the multiplication equivalent of sigma (the summation symbol) be? $$\sum$$ I want to do a series of multiplication of terms.... instead of addition...

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Can you reduce the size of the image? – user17762 Mar 4 '11 at 0:27
capital pi for product (like capital sigma for sum), for instance: $$\sin(\pi z)=\pi z\prod_{n=1}^{\infty}\Big(1-\frac{z^2}{n^2}\Big)$$ – yoyo Mar 4 '11 at 3:23
what is this operation called? – tekknolagi Mar 4 '11 at 6:13

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up vote 8 down vote

It's a capital pi (for product): $\prod$. You can sometimes find useful symbols and guess what they mean from their $\LaTeX$ names, although I guess the most reliable way to find useful, well-known symbols is just to read a lot of math.

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There is also the table of mathematical symbols on wikipedia. – Harry Stern Mar 3 '11 at 23:42
Ah! That's much better than what I said. – Qiaochu Yuan Mar 3 '11 at 23:49
@tekknolagi By the way, to typeset this symbol in LaTeX, one would use the \prod command rather than the greek symbol \Pi (or \pi). This is similar to preferring \sum to \Sigma. – Srivatsan Aug 31 '11 at 11:44
up vote 2 down vote

I google "latex symbols" when I need something I can't recall. That'll give you many lists and tips. For example, if you choose the first hit, the AoPS list and look for the sum symbol you'll find the product symbol right below it. This is but a simple example of a general technique of exploiting organization and classification on the web to discover information about similar items.

For the inverse, when you know the symbol but not the name there is deTeXify which let's you draw the symbol and does OCR to find the name. For deeper questions there's the (La)Tex SE site.

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