12.求下列各函数在指定点z0处的泰勒展式,并指出它们的收敛半径:-|||-(1) dfrac (z-1)(z+1), _(0)=1-|||-(2) dfrac (z)((z+1)(z+2)) . _(0)=2;-|||-(3) dfrac (1)({2)^2} , _(0)=-1;-|||-(4) dfrac (1)(4-3z), _(0)=1+i;-|||-(5)tanz, _(0)=dfrac (pi )(4);-|||-(6)arctanz, _(0)=0.