Theorem rmotru 49640

Description: Two ways of expressing "at most one" element. (Contributed by Zhi Wang, 19-Sep-2024.) (Proof shortened by BJ, 23-Sep-2024.)

Assertion

Ref	Expression
rmotru	⊢ (∃*𝑥 𝑥 ∈ 𝐴 ↔ ∃*𝑥 ∈ 𝐴 ⊤)

Proof of Theorem rmotru

Step	Hyp	Ref	Expression
1		tru 1574	. . . 4 ⊢ ⊤
2	1	biantru 539	. . 3 ⊢ (𝑥 ∈ 𝐴 ↔ (𝑥 ∈ 𝐴 ∧ ⊤))
3	2	mobii 2578	. 2 ⊢ (∃*𝑥 𝑥 ∈ 𝐴 ↔ ∃*𝑥(𝑥 ∈ 𝐴 ∧ ⊤))
4		df-rmo 3371	. 2 ⊢ (∃*𝑥 ∈ 𝐴 ⊤ ↔ ∃*𝑥(𝑥 ∈ 𝐴 ∧ ⊤))
5	3, 4	bitr4i 281	1 ⊢ (∃*𝑥 𝑥 ∈ 𝐴 ↔ ∃*𝑥 ∈ 𝐴 ⊤)

This proof depends on syntax axioms:   ↔ wb 209   ∧ wa 401  ⊤wtru 1571   ∈ wcel 2146  ∃*wmo 2567  ∃*wrmo 3370

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041

This proof depends on definitions:  df-bi 210  df-an 402  df-tru 1573  df-ex 1813  df-mo 2569  df-rmo 3371

This theorem is used by:  reutruALT  49642  mosn  49650