傅里叶复指教级撤证法2 由欧拉公式 cos(n@ot+onsI (e1(y+1)+e-mn+) x()=4+∑4,cos(nat+g) x()=4+∑4(e 1 nj(not+on)+e j(not+g, n- =A+∑41(ee ern +e Jnaoto-j9,X 傅里叶复指数级数证法 2 0 0 ( ) 1 ( ) cos n n n x t A A n t    = = + +  •由欧拉公式： 0 0 j( ) j( ) 0 1 cos( ) (e e ) 2 n t n t n n n t n       + − + + = + 0 0 j( ) j( ) 0 1 1 ( ) (e e ) 2 n n n t n t n n x t A A      + − + = = + +  0 0 j j j j 0 1 1 (e e e e ) 2 n n n t n t n n A A      − − = = + + 