How can I make a big summation sign?
\begin{align}
\cos x = \sum\limits_{n=0}^{\infty} \frac{(ix)^{2n}}{(2n)!}
\end{align}
this is the code which I'm using for summation
[Tex/LaTex] making a big summation sign
math-mode
Related Solutions
The usual thing to do is replace ( with \left( and ) with \right), which automatically expand to fit the material between them. Note that every \left... requires a \right... (but the type of bracket may be different, i.e. \left(...\right] also works).
I would typeset your equation as
\begin{equation*}
\sum_{i=1}^n i = \left(\sum_{i=1}^{n-1} i\right) + n =
\frac{(n-1)(n)}{2} + n = \frac{n(n+1)}{2}
\end{equation*}
For manual control of sizes (most of the time you won't need these)
( \big( \Big( \bigg( \Bigg(
produce
I see no reason for making the summation symbol larger. Big matrices are no excuse.
If you really want to ignore this advice, here's the correct way to proceed with \mathlarger:
\documentclass[11pt,a4paper,oneside]{report}
\usepackage{fouriernc}
\usepackage{mathtools}
\usepackage{relsize}
\begin{document}
\begin{equation}
c_{ij}=\sum_{i'<i'',\,j'<j''}
\begin{pmatrix}
i&i'&i''\\1&2&3
\end{pmatrix}
\end{equation}
\begin{equation}
c_{ij}=\mathop{\mathlarger{\sum}}_{i'<i'',\,j'<j''}
\begin{pmatrix}
i&i'&i''\\1&2&3
\end{pmatrix}
\end{equation}
\begin{equation}
c_{ij}=\mathop{\mathlarger{\mathlarger{\sum}}}_{i'<i'',\,j'<j''}
\begin{pmatrix}
i&i'&i''\\1&2&3
\end{pmatrix}
\end{equation}
\end{document}
I avoided the triple \mathlarger as it's incredibly awful and I've no doubt that the top one is right.
Note that i' is equivalent to i^{\prime}; for a double prime either use
i^{\prime\prime}
or the simpler
i''
but never i^{''}. Also a thin space \, after the comma in the summation limit is better.
Best Answer
You can use the command
\mathlargerof therelsizepackage. It increases the size and it can be nested. For example:.....