Enter functions as expression in terms of "x". Usual rules apply. For exponents use "^", e.g. "e^x".
Scroll the wheel to change the number of terms in the sum.
Good functions to try (non-specified coefficients are 0)
Odd Step: sin coefficient = (2/pi)*(1-(-1)^n)/n
Even Step: cos coefficient = (4/pi)*sin(n*pi/2)/n
Hat: cos coefficient = (2/pi)*(1-(-1)^n)/n
Delta Function: constant coefficient = cos coefficient = 1