Theorem trss 4140

Description: An element of a transitive class is a subset of the class. (Contributed by NM, 7-Aug-1994.)

Assertion

Ref	Expression
trss	⊢ (Tr 𝐴 → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))

Proof of Theorem trss

Dummy variable 𝑥 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eleq1 2259	. . . . 5 ⊢ (𝑥 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝐵 ∈ 𝐴))
2		sseq1 3206	. . . . 5 ⊢ (𝑥 = 𝐵 → (𝑥 ⊆ 𝐴 ↔ 𝐵 ⊆ 𝐴))
3	1, 2	imbi12d 234	. . . 4 ⊢ (𝑥 = 𝐵 → ((𝑥 ∈ 𝐴 → 𝑥 ⊆ 𝐴) ↔ (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴)))
4	3	imbi2d 230	. . 3 ⊢ (𝑥 = 𝐵 → ((Tr 𝐴 → (𝑥 ∈ 𝐴 → 𝑥 ⊆ 𝐴)) ↔ (Tr 𝐴 → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))))
5		dftr3 4135	. . . 4 ⊢ (Tr 𝐴 ↔ ∀𝑥 ∈ 𝐴 𝑥 ⊆ 𝐴)
6		rsp 2544	. . . 4 ⊢ (∀𝑥 ∈ 𝐴 𝑥 ⊆ 𝐴 → (𝑥 ∈ 𝐴 → 𝑥 ⊆ 𝐴))
7	5, 6	sylbi 121	. . 3 ⊢ (Tr 𝐴 → (𝑥 ∈ 𝐴 → 𝑥 ⊆ 𝐴))
8	4, 7	vtoclg 2824	. 2 ⊢ (𝐵 ∈ 𝐴 → (Tr 𝐴 → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴)))
9	8	pm2.43b 52	1 ⊢ (Tr 𝐴 → (𝐵 ∈ 𝐴 → 𝐵 ⊆ 𝐴))

Syntax hints:   → wi 4   = wceq 1364   ∈ wcel 2167  ∀wral 2475   ⊆ wss 3157  Tr wtr 4131

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 710  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-bndl 1523  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549  ax-ext 2178

This theorem depends on definitions:  df-bi 117  df-tru 1367  df-nf 1475  df-sb 1777  df-clab 2183  df-cleq 2189  df-clel 2192  df-nfc 2328  df-ral 2480  df-v 2765  df-in 3163  df-ss 3170  df-uni 3840  df-tr 4132

This theorem is referenced by:  trin  4141  triun  4144  trintssm  4147  tz7.2  4389  ordelss  4414  trsucss  4458  ordsucss  4540  ctinf  12647