4.8 将下列各函数在指定圆环内展开为洛朗级数:-|||-(1) dfrac (z+1)({z)^2(z-1)} ,lt 1=1lt 1,1lt 1=1lt +infty ;-|||-(2) ^2(e)^dfrac (1{x)},0lt |z|lt +infty ;-|||-(3) dfrac ({z)^2-2z+5}((z-2)({z)^2+1)},1lt |z|lt 2 ;-|||-(4) cos dfrac (1)(1-z),0lt |z-1|lt +infty .