21.指出下列各题中点z的轨迹或所在范围,并作图:-|||-(1) |z-5|=6 ;-|||-(2) |z+2i|geqslant 1 ;-|||-(3) Re(z+2)=-1 ;-|||-(4) (i)=3 ;-|||-(5) |z+i|=|z-i| ;-|||-(6) |z+3|+|z+1|=4 ;-|||-(7) ln (z)leqslant 2 ;-|||-(8) |dfrac (z-3)(z-2)|geqslant 1 ;-|||-(9) lt arccos xlt pi ;-|||-(10) (z-i)=dfrac (pi )(4) -