Theorem pssned

Description: Proper subclasses are unequal. Deduction form of pssne . (Contributed by David Moews, 1-May-2017)

	Ref	Expression
Hypothesis	pssssd.1	|- ( ph -> A C. B )
Assertion	pssned	|- ( ph -> A =/= B )

Proof

Step	Hyp	Ref	Expression
1		pssssd.1	|- ( ph -> A C. B )
2		pssne	|- ( A C. B -> A =/= B )
3	1 2	syl	|- ( ph -> A =/= B )