For this applet you set the Fourier Series Coefficients and then guess the function. [br]The domain is [i]-L<x<L[/i] . The slider controls the number of terms to sum. For the coefficients you can enter a function containing [i]n[/i] and optionally [i]L[/i] . The coefficients should get smaller as [i]n[/i] increases.The solid blue curve shows the Fourier Series partial sum and the dashed green curve shows your guess at the function.