# Cannot find how to write infinity [duplicate]

I am new here. How do I write an infinity symbol above summation symbol. I do not know how to write formula on this site. How do I write series formula? I could figure out how to write summation, but how do I write infinity here above summation symbol? I could not find it. Thanks.

• In particular, point (7), titled "Sums and integrals."
– user296602
Feb 12 '18 at 18:13

## 1 Answer

We use MathJax formatting on this site. By and large, symbols are the same as they are in LaTeX. LaTeX has a number of excellent resources, including DeTexify which allows you to draw symbols and then used machine learning to decide what code you are looking for. The Not So Short Introduction to LaTeX is also an excellent resource. You can also click "edit" on any question to view its source code, which is an excellent way to learn.

To answer your specific question, we can do \infty to produce $\infty$ and \sum_{i=0}^{\infty}a_i to produce $\sum_{i=0}^{\infty}a_i$. Using two \\$ in a row, like this $$\sum_{i=0}^{\infty}a_i$$ produces the same equation, but set on it's own line $$\sum_{i=0}^{\infty}a_i$$