How to use greek symbol for sum in the latex document

Question

I want to write a formula that has the greek "sum" (Σ) symbol. How can I write the "sum" symbol in latex

Answer 1

You can use \sum to write the greek "sum" (Σ) symbol.

Here is an example:

\alpha = \frac{\sum_{j=1}^k \alpha_j}{k}

The above formula calculates the average alpha, the sum of k alphas divided by k.