Keywords: Square Wave Fourier Series.svg A square wave with period 1 and amplitude 4 and two Fourier series approximations with k 5 and 15 from the equation <br> <math>f t 2 - \frac 4 \pi \sum_ n 1 k \frac -1 n - 1 n \sin 2 \pi n t </math><br> self-made Inkscape 2008-03-13 Inductiveload Fourier series |