ClearConcept — A-Level Revision

Specification Reference

De Morgan's laws

Standard

Plain English

Logical equivalences describing relationships between AND, OR, and NOT operators. De Morgan's laws enable Boolean expression simplification.

Formula

NOT (A AND B) = (NOT A) OR (NOT B); NOT (A OR B) = (NOT A) AND (NOT B)

public

Real World

Google's search engine uses De Morgan's laws to optimise query filters — searching for 'NOT (Python AND Java)' is internally rewritten to 'NOT Python OR NOT Java' to match its index structure faster.

tips_and_updates

Exam Focus

Remember: NOT flips the operator (AND becomes OR) and negates each input — practise by verifying with truth tables.

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