Different way of writing intersection in relational algebra

U开发者_StackOverflow社区sing basic operators, derive the additional operator intersection.

R ∩ S = ?

I thought it might be: (R ∪ S) - ((R -S) ∪ (S -R)) but I also think there might be an easier way of doing it?

A intersected with B is equal to A - (A - B) or equivalenty B - (B - A)

R ∩ S is also equal to ~( (~R) ∪ (~S) )

where ~A is the complement of A