Originally Posted by

**monster** I'm new to topology and have just started looking at whether spaces are topologies or not, I've come across a question where i have to show a space is a topology on N and am not sure how to approach it,

T = {T_{n }:n ∊N} ∪ {∅} where T_{n }={m ∊N:m ≥ n}

I am supposed to prove T is a topology on N (natural numbers).

Clearly condition T1 is satisfied as T has the empty set and N, but i'm not sure how to approach showing T2 and T3 are satisfied any help would be great, cheers.