Thread: is the set F = {A|A or A^c is finite} over R a sigma algebra?

define

My anwser: Yes as
a) if empty set = then A = which belongs to F
b) WLOG if A is finite let B = is uncoutnable but is fintire thus B belongs in F.
c) a union of finite sets is finite thus belong in F

Originally Posted by rosh3000

define

My anwser: Yes as
a) if empty set = then A = which belongs to F
b) WLOG if A is finite let B = is uncoutnable but is fintire thus B belongs in F.
c) a union of finite sets is finite thus belong in F

For each is it true that

Is it true that

Yes clearly finite,
No union is infinte and complement is uncountable infinte thus not in f

Thank you