Sigma Algebra generated by a Class

[@AliceWandering-c8w]

At 4:18, Bn formulas seems wrong

[@gayathrivarma7163]

yea, it should be the other way

[@gayathrivarma7163]

B_3 = A_3 \ A_1 U A_2

[@sonigahlawat1414]

Yes right But after correction how to prove this

[@mikelindenstrauss.1955]

@@sonigahlawat1414 If you use the revised formulae for B_n it would still be the intersection of finitely many elements in the algebra and as any algebra is closed under finite intersections we are through.