# Discrete and continuous problems

1. Jun 4, 2007

### haiha

Hi all,

There are some dificult problems with discrete argument n that will be very easy if I can change it to continuous argument x. But I do not know what is the condition for that.
For example: to calculate the sum of a1+a2 +a3+...an. when n goes to infinity, can I make it as S=integral of a(x) from xo to infinity ?

Thanks

2. Jun 5, 2007

### mathman

It depends very much on how you define a(x) for x not an integer.

3. Jun 5, 2007