Nug: Cardinality Revisited Definition: Lub cardinality ntawm lub teeb Ais sib npaug rau cardinality ntawm ib teev B, denoted |A|=|B], yog thiab tsuas yog muaj ib tug bijection ntawm A mus rau B. Yog hais tias muaj kev txhaj tshuaj los ntawm A mus rau B, lub cardinality ntawm A yog tsawg dua los yog tib yam li cardinality ntawm B thiab peb sau A Bl.
Yuav ua li cas yog cardinality?
Qhov loj ntawm qhov finite set (tseem hu ua nws cardinality) yog ntsuas los ntawm cov ntsiab lus nws muaj. Nco ntsoov tias suav tus naj npawb ntawm cov ntsiab lus hauv ib qho nyiaj tau los ua 1-1 kev sib txuas lus ntawm nws cov ntsiab lus thiab cov lej hauv {1, 2, …, n}.
Cardinality piv txwv yog dab tsi?
Lub cardinality ntawm ib lub teeb yog ntsuas ntawm ib lub teeb qhov loj, lub ntsiab lus ntawm cov khoom hauv lub teeb. Piv txwv li, lub teeb A={ 1, 2, 4 } A=\{1, 2, 4} A={1, 2, 4} muaj ib tug cardinality ntawm 3 rau peb lub ntsiab lus uas muaj nyob rau hauv nws.
Yuav ua li cas yog cardinality ntawm ib tug ∅?
3. Lub cardinality ntawm lub khoob teeb {} yog 0. 0. Peb sau {}=0 uas yog nyeem raws li "lub cardinality ntawm lub khoob teeb yog xoom" los yog "tus naj npawb ntawm cov ntsiab lus nyob rau hauv lub khoob yog xoom. "
Yuav ua li cas koj pom lub cardinality ntawm ib lub teeb?
Xav txog ib lub teeb A. Yog tias A tsuas muaj tus lej kawg nkaus xwb, nws cardinality tsuas yog tus naj npawb ntawm cov ntsiab lus hauv A. Piv txwv li, yog A={2, 4, 6, 8, 10}, ces |A|=5.
