## Partial Differential Equations

f(x) is a periodic real valued function with period 2π. Assume f can be represented as :
f(x) ~ SUM (from n = -infinity to + infinity) [An*e^(inx)]
where An are complex constants. show that :
Am = (1/2π).......

I do not know how to start or solve this problem so any help would be greatly appreciated.

many thanks