, n
Now, we know that for any event A,
A = A ∩ S
= A ∩ (E1 ∪ E2 ∪ ∪ En)
= (A ∩ E1) ∪ (A ∩ E2) ∪ ∪ (A ∩ En)
Also A ∩ Ei and A ∩ Ej are respectively the subsets of Ei and Ej We know that
Ei  and Ej are disjoint, for i
≠j
, therefore, A  ∩ Ei and A  ∩ Ej  are also disjoint for all
i ≠ j,  i, j = 1, 2,