### Answer:

There are some ways to do that. First, you have to write β\sumβ and the sign will be displayed. If you want to add something after this sign you can do that by writing β\sum_{i=0}^{n}β or β\sum\limits_{i=0}^{n}β. Another way is to display sums separately from the text by typing β\displaystyle\sumβ so that the sum sign appears. Then yoy may add any formula you need: β\displaystyle\sum_{i=0}^{n}β. But if you just need a small sign you can also copy and past it from HTML Character Entity Reference Chart.

It’s easy!