Inclusion–exclusion for overlapping sets
For finite A,B, |A∪B|=|A|+|B|−|A∩B|.
Key knowledge
For finite A,B, |A∪B|=|A|+|B|−|A∩B|. For three sets add their individual sizes, subtract all three pairwise intersections, and add the triple intersection.
Conditions and scope
- Count elements of a union once; all intersections use the same underlying objects.
- This record states the two- and three-set versions.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Section 1.1 inclusion/exclusion subsection, union formula and three-set construction.
2026-10-10 · Independent AI editorial review: All241 compact claims, hypotheses, displayed equations/conventions and all596 origin semantic links read; entire241-entry author exact-source inspection matrix and declared limitations reviewed. Prior105 actual inherited Mathematics/Information records read for whole-inventory breadth. Targeted independent primary sections are listed below; this does NOT claim every cited source body or every proof was independently re-read. This is AI reference-content review, not human disciplinary certification, exhaustive textbook reproduction or experimental replication. Receipt: mathematics-information-independent-content-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- math-inclusion-exclusion
- Revision
- university-core.1
- Structured reference record
- University core expansion