Fourier Series Calculator online help you:
[✔] To expand a function in Fourier series at a interval of x
[✔] See result of the expand on the graph - the function and several nearly fourier series

Support:

[✔] Supported all math symbols and functions. For example: sin(x), cos(x), exp(x), tan(x), ctan(x), sqrt(x) and other.
[✔] Suported complex variables
[✔] A variety of arguments and options: x, y, n, a, b, c and etc.

The Calculator contain several features:
[✔] Several examples
[✔] Сorrect input expression errors

Examples of Fourier Series:
x*exp(-x)