Theorem supmax 8915

Description: The greatest element of a set is its supremum. Note that the converse is not true; the supremum might not be an element of the set considered. (Contributed by Jeff Hoffman, 17-Jun-2008.) (Proof shortened by OpenAI, 30-Mar-2020.)

Hypotheses

Ref	Expression
supmax.1	⊢ (𝜑 → 𝑅 Or 𝐴)
supmax.2	⊢ (𝜑 → 𝐶 ∈ 𝐴)
supmax.3	⊢ (𝜑 → 𝐶 ∈ 𝐵)
supmax.4	⊢ ((𝜑 ∧ 𝑦 ∈ 𝐵) → ¬ 𝐶𝑅𝑦)

Assertion

Ref	Expression
supmax	⊢ (𝜑 → sup(𝐵, 𝐴, 𝑅) = 𝐶)

Distinct variable groups:   𝑦,𝐴   𝑦,𝐵   𝑦,𝐶   𝑦,𝑅   𝜑,𝑦

Proof of Theorem supmax

Dummy variable 𝑧 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		supmax.1	. 2 ⊢ (𝜑 → 𝑅 Or 𝐴)
2		supmax.2	. 2 ⊢ (𝜑 → 𝐶 ∈ 𝐴)
3		supmax.4	. 2 ⊢ ((𝜑 ∧ 𝑦 ∈ 𝐵) → ¬ 𝐶𝑅𝑦)
4		supmax.3	. . 3 ⊢ (𝜑 → 𝐶 ∈ 𝐵)
5		simprr 772	. . 3 ⊢ ((𝜑 ∧ (𝑦 ∈ 𝐴 ∧ 𝑦𝑅𝐶)) → 𝑦𝑅𝐶)
6		breq2 5034	. . . 4 ⊢ (𝑧 = 𝐶 → (𝑦𝑅𝑧 ↔ 𝑦𝑅𝐶))
7	6	rspcev 3571	. . 3 ⊢ ((𝐶 ∈ 𝐵 ∧ 𝑦𝑅𝐶) → ∃𝑧 ∈ 𝐵 𝑦𝑅𝑧)
8	4, 5, 7	syl2an2r 684	. 2 ⊢ ((𝜑 ∧ (𝑦 ∈ 𝐴 ∧ 𝑦𝑅𝐶)) → ∃𝑧 ∈ 𝐵 𝑦𝑅𝑧)
9	1, 2, 3, 8	eqsupd 8905	1 ⊢ (𝜑 → sup(𝐵, 𝐴, 𝑅) = 𝐶)

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 399   = wceq 1538   ∈ wcel 2111  ∃wrex 3107   class class class wbr 5030   Or wor 5437  supcsup 8888

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-10 2142  ax-11 2158  ax-12 2175  ax-ext 2770

This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-3or 1085  df-3an 1086  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2070  df-mo 2598  df-eu 2629  df-clab 2777  df-cleq 2791  df-clel 2870  df-nfc 2938  df-ne 2988  df-ral 3111  df-rex 3112  df-reu 3113  df-rmo 3114  df-rab 3115  df-v 3443  df-sbc 3721  df-dif 3884  df-un 3886  df-in 3888  df-ss 3898  df-nul 4244  df-sn 4526  df-pr 4528  df-op 4532  df-uni 4801  df-br 5031  df-po 5438  df-so 5439  df-iota 6283  df-riota 7093  df-sup 8890

This theorem is referenced by:  suppr  8919  gsumesum  31428  supfz  33073  mblfinlem2  35095