# Homework Help: Evaluate summation

1. Apr 25, 2010

### annoymage

1. The problem statement, all variables and given/known data

evaluate
$$\sum$$$$\frac{1}{e^n}$$ from 0 -> infinity

2. Relevant equations

N/A

3. The attempt at a solution

from what i've learn, i can calculate summation i in form

$$\sum$$na ,a is integer
or
$$\sum$$ f(n+1)-f(n)

but how to make 1/e^n in any those form?
can give me any clue please
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Apr 25, 2010

### LCKurtz

Hint: Think about geometric series

3. Apr 25, 2010

### annoymage

$$\sum$$($$\frac{1}{e}$$)n

yes, why am i so stupid didn't think of that =.=

thank you very much