# Math Help - Sigma or sum with index or indicies

1. ## Sigma or sum with index or indicies

I know how to create a sigma sign for a sum - use the large operator \sum

But how do you show an index, say i running from, say, 1 to n

Further, how do you neatly create two or more indices

Would appreciate any help in this matter

Peter

2. ## Re: Sigma or sum with index or indicies

Originally Posted by Bernhard
I know how to create a sigma sign for a sum - use the large operator \sum
But how do you show an index, say i running from, say, 1 to n
Further, how do you neatly create two or more indices
[TEX]\sum\limits_{k = 2}^{10} {\ln (k)} [/TEX] gives $\sum\limits_{k = 2}^{10} {\ln (k)}~.$

3. ## Re: Sigma or sum with index or indicies

The formula mode (inline or display) determined whether operator indices are placed as regular sub/superscripts or directly below/above the operator. You can change this behavior using \limits and \nolimits between an operator and an index.

Concerning two or more indices (I assume something like 0 ≤ i ≤ m and 0 < j < n), you can either write them in one line or use the following example from The LaTeX Companion, 2nd edition (8-3-5, p. 488):

$\sum_{\substack{0 \le i \le m \\ 0 < j < n}} P(i, j)$.

There is also an example
Code:
\sum_{\begin{subarray}{l}  i \in \Lambda   \\
0 \le i \le m   \\
0 < j < n
\end{subarray}}  P(i, j)
but it does not work on MHF.

4. ## Re: Sigma or sum with index or indicies

Originally Posted by Bernhard
I know how to create a sigma sign for a sum - use the large operator \sum

But how do you show an index, say i running from, say, 1 to n

Further, how do you neatly create two or more indices

Would appreciate any help in this matter

Peter
Use \sum_{lower limit}^{upper limit} for $\displaystyle \sum_{\textrm{lower limit}}^{\textrm{upper limit}}$.