⑩天掌 Teaching Plan on Advanced Mathematics o 级数收敛于 1+11+(-1) 2 当x≠k丌时级数收敛于f(x) 计算傅里叶系数如下: f(x)cos nxd 丌-丌 (1)cos ndx cos nr d x 0 =0(n=1,2,…) tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 级数收敛于 0, 2 1 ( 1) 2 1 1 = + − = − + 当 x  k 时级数收敛于 f ( x). 计算傅里叶系数如下： − =    an f (x)cosnxdx 1   = − +  −     0 0 1 cos 1 ( 1)cos 1 nxdx nxdx = 0 (n = 1,2, );