Theorem undm

Description: De Morgan's law for union. Theorem 5.2(13) of Stoll p. 19. (Contributed by NM, 18-Aug-2004)

	Ref	Expression
Assertion	undm	⊢ ( V ∖ ( 𝐴 ∪ 𝐵 ) ) = ( ( V ∖ 𝐴 ) ∩ ( V ∖ 𝐵 ) )

Proof

Step	Hyp	Ref	Expression
1		difundi	⊢ ( V ∖ ( 𝐴 ∪ 𝐵 ) ) = ( ( V ∖ 𝐴 ) ∩ ( V ∖ 𝐵 ) )