Engineering related applications of infinite series

I have to do a project on infinite series where I make a poster about them and I need to have it involve an application of the infinite series in something engineering related. Unfortunately, I'm fresh out of ideas. I know of how it could be applied to medicine, perhaps a pill that has a certain half life and you take the pill every few hours so you have to know how much accumulates in the body, however, this is irrelevant as I need engineering applications :P

HELP!

thanks,

Anthony