For the function f(x)={−2,−π<x<02,0<x<π The value of an in the Fourier series expansin of f(x) is
an=1π∫π−πf(x)cosnxdx =1π[∫0−π(−2)cosnxdx+∫π0(2)cosnxdx] =1π[(−2)(sinnxn)0−π+(2)(sinnxn)π0] = 0
Let f(x)={−π,if−π<x≤0π,if0<x≤π be a periodic function of period 2π. The coefficient of sin5x in the Fourier series expansion of f(x) in the interval [−π,π] is
f(x) =π4+2π[cosx12+cos3x32+....]+[sinx1+sin2x2+sin3x3+....] The convergence of the above Fourier series at x = 0 gives