Fourier series graph and series representation help

The Fourier series is a series representation of a periodic function in terms of sines and cosines.

The Fourier series representation of the function f(x) = { 1, 0 < x < π... −1, −π < x < 0 is

4/π ( sin x/1 + sin 3x/3 + sin 5x/5 + sin 7x/7 + . . . )

Plot on the same graph the function f (x) and its series representation, using the four terms shown.

This is my a question on my first homework assignment but my professor only went over the very simple stuff. I couldn't find any examples.