lesson5 (乌里松引理，紧致性 (上))

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2、A≡0,f

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5、x6∈Ur}0ëY§,éx∈U0,-f(x)=0.dÊÚnf3mëY"?x∈Uc9f(x)V,ef(x)∈(0,1),0K3a,s,t,b∈R={ri}¦a

6、R¦0

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9、m8Uα,SαUα´48¶K¡BlÑ"Bing-Nagata-SmirnovÝÝÝþþþzzz½½½nnnµµµ(Ø)÷vT3únHausdorffmXÝþzc=3XXlÑf8xB1,B2,...,S¦

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11、

12、d(x,y)>1/k},K{Uk}vkkfCX§ÏdAØ;"eAÃ.§Uk=[−k,k],K{Uk}vkkfCX§ÏdAØ;"~~~µµµn¥¡Sn;"···KKKµµµ;m3ëYNe8;"~~~µµµ¡T2;§Ï§ÓuS1×S1,ϧ´[0,1]×[0,1]"~~~µµµ;mþëY¼êk.§¿UÚ§Ïf(X)⊆E1;"gµP50:3,4.P59:4,8,9