Determining fourier series coefficients graphically

THE ACCURACY of the Fourier series coefficients when determined by the equation
¹

$B_{n} = {2 \over m} displaystyle\sum^{m}_{1} \left[y_{k} \sin \ n \left(k - {1 \over 2}\right){2 \pi \over m} \right]$
should receive some consideration.