So I've seen that pi can be written as a series:
http://upload.wikimedia.org/math/4/b...be1ac3be60.png
So pi = 4/1 - 4/3 + 4/5 - 4/7 + ...
Now I know that Q is an ordered field so if a and b are in Q, if I add them, the result a+b is another element in Q.
But if I sum up infinitely many rational numbers I can get an irrational? Wondering how this works.