2.6.2.32 Trigonometric Fourier series
condition: Calculate the coefficient \( a_{4} \) of the expansion of the function \( f(x)=\left\{\begin{array}{cc}-3+x, & x \in[0 ; 3] \\ 3, & x \in(3 ; 6]\end{array}\right. \) into a Fourier series in terms of cosines on the segment \( [0 ; 6] \).
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.