2.6.2.27 Trigonometric Fourier series
condition: Expand the function \( f(x)=3 x \) into a Fourier series on the interval \( [0,4] \) along the cosines of arcs that are multiples of \( \pi x / 4 \).
Trigonometric Fourier series - calculation of Fourier coefficients, expansion of functions in cosines and sines, plotting graphs of the sum of the Fourier series using the Dirichlet theorem, as well as graphs of partial sums.