$$f(x)=\left\{\begin{array}{l l} 0,\quad x \in [-L,0[\\ 1,\quad x \in [0,L] \end{array}\right.$$
I need to know in which intervals the sum of the Fourier series is "equal to the function $f(x)$".
Please help and help me understand how to solve it because I have four exercises like this... Thanks