Sigma Notation

This symbol (called Sigma) means "sum up"

I love Sigma, it is fun to use, and can do many clever things.

So means to sum things up ...

Sum What? Sum whatever appears after the Sigma:				so we sum n
But What is the Value of n ? The values are shown below and above the Sigma:				it says n goes from 1 to 4, so that is 1, 2, 3 and 4
OK, Let's Go ... So now we add up 1,2,3 and 4:

Here it is in one diagram:

More Powerful

But Σ can do more powerful things than that!

You could square n each time and sum the result:

And this next one means "add up the first four terms in the sequence 2n+1":

And you don't have to use n. Here we use i and sum up i × (i+1), going from 1 to 3:

And you can start and end with any number. Here we go from 3 to 5:

Try some of your own!

Why is it called "Sigma"

Sigma is the upper case letter S in Greek. And S stands for Sum.

Now you get the idea, you might like to read the more advanced topic Partial Sums.