Theorem psstrd 3610

Description: Proper subclass inclusion is transitive. Deduction form of psstr 3607. (Contributed by David Moews, 1-May-2017.)

Hypotheses

Ref	Expression
psstrd.1
psstrd.2

Assertion

Ref	Expression
psstrd

Proof of Theorem psstrd

Step	Hyp	Ref	Expression
1		psstrd.1	. 2
2		psstrd.2	. 2
3		psstr 3607	. 2
4	1, 2, 3	syl2anc 661	1

Syntax hints:  ->wi 4  C.wpss 3476

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1618  ax-4 1631  ax-5 1704  ax-6 1747  ax-7 1790  ax-10 1837  ax-11 1842  ax-12 1854  ax-13 1999  ax-ext 2435

This theorem depends on definitions:  df-bi 185  df-an 371  df-tru 1398  df-ex 1613  df-nf 1617  df-sb 1740  df-clab 2443  df-cleq 2449  df-clel 2452  df-ne 2654  df-in 3482  df-ss 3489  df-pss 3491