Sum Formulas and Sigma Notation.

There was more stuff to learn about geometric sequences. The New and Innovative thing was called sigma notation:


What does this all mean?

Well . . . how about the sum a sigma? It'll ask us to expand it:


t1 + t2 + t3 + t4 . . .

Evaluate n = 5, k = 1, 2^k

= 2 + 4 + 8 + 16 + 32

in summation notation:

How do we get the sum of a sequence without adding all the numbers? We have a formula for that.

Sn = t1 (1 - r^n) / 1 - r

We can use this formula to measure the sum of a sequence without having to go through the tedium of adding every number in there.