⑩天掌 Teaching Plan on Advanced Mathematics o 利用傅氏展开式求级数的和 f(x)= c0s(2n-1)x, 2=(2n-1) 当x=0时,f(0)=0,元2 1+- 325 设a=1+2+2+2+…, o,=1++ 52× 8 tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 利用傅氏展开式求级数的和 cos(2 1) , (2 1) 4 1 2 ( ) 1  2  = −  − −  = n n x n  f x 当x = 0时, f (0) = 0, = + + +  2 2 2 5 1 3 1 1 8 , 4 1 3 1 2 1 1 设 = + 2 + 2 + 2 + ), 8 ( 5 1 3 1 1 2 1 2 2   = + + + =