当x≠π时,收敛于f(x).和函数图象为 u(t)cos ntd T GEmcos nt 兀0 Em cos ndt =0 (n=0 u(tsinntdt (Em)sin ntt+Em ntt T当x  k时, 收敛于f (x). 和函数图象为 o t u −  m E − Em    − a = u t ntdt n ( )cos 1    −  + −  = 0 0 cos 1 ( )cos 1 E ntdt E ntdt m m = 0 (n = 0,1,2, )    − b = u t ntdt n ( )sin 1    −  − +  = 0 0 sin 1 ( )sin 1 E ntdt E ntdt m m