题目5.证明 (z)=cos (z+dfrac (1)(z)) 用z的幂表出的洛朗展开式中的系数为-|||-_(n)=dfrac (1)(2pi )(int )_(0)^2pi cos (2cos theta )cos ntheta dtheta =0 ,±1 ,±2 .....题目解答答案