Le capo du troupeau des s\'eries de Fourier
  A glimpse at $\sum{{\sin(kx)}\over{k}}$ gives a few lines exposition of Fourier series's quadratic mean convergence for square integrable functions and Dirichlet's convergence theorem of the Fourier serie of a piecewise differentiable function with integrable derivative. 
Alexis Marin
math.CA