1.判断下列平面点集中哪些是开集、闭集、有界集、区域,并分别指出它们的聚点与界点:-|||-(1) [ a,b)times [ c,d] ;-|||-(2) (x,y)|xyneq 0 ;-|||-(3) (x,y)|xy=0 ;-|||-(4) (x,y)|ygt {x)^2} ;-|||-(5) (x,y)|xlt 2,ylt 2,x+ygt 2 ;-|||-(6) (x,y)|{x)^2+(y)^2=1或y=0,0leqslant xleqslant 1} ;-|||-(7) |(x,y)|(x)^2+(y)^2leqslant 1或y=0,1leqslant xleqslant 2 ;-|||-(8)((x,y)|x,y均为整数);-|||-(9) (x,y)|y=sin dfrac {1)(x),xgt 0} .