1.5 Union, Intersection, Difference

Sets

Union

• the union of A and B is the set:
  • A $\cup$ B = { x: x $\in$ A or x $\in$ B}

Intersection

• the intersection of A and B is the set:
  • A $\cap$ B = *A $\cap$ B = { x: x $\in$ A and x $\in$ B}

Difference

• the difference of A and B is the set:
  • $A-B$ = { $x$: $x\in A$ and $x\notin B$ }

Inclusion - Exclusion Principle

• |A $\cup$ B| = |A| + |B| - |A $\cap$ B|