PIE (Principle of Inclusion-Exclusion) AUB|=A+|B-A∩B AUBUC=A+B+C -A∩B-A∩C1-|BnC1 +|A∩B∩C C BnC AnC AnBnC A B AnBPIE (Principle of Inclusion-Exclusion) |A ￾ B| = |A| + |B|￾|A ⇥ B| |A ￾ B ￾ C| = |A| + |B| + |C| ￾|A ⇥ B| ￾ |A ⇥ C| ￾ |B ⇥ C| +|A ￾ B ￾ C|