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Definition df-ltxr 7581
 Description: Define 'less than' on the set of extended reals. Definition 12-3.1 of [Gleason] p. 173. Note that in our postulates for complex numbers, <ℝ is primitive and not necessarily a relation on ℝ. (Contributed by NM, 13-Oct-2005.)
Assertion
Ref Expression
df-ltxr < = ({⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ ∧ 𝑥 < 𝑦)} ∪ (((ℝ ∪ {-∞}) × {+∞}) ∪ ({-∞} × ℝ)))
Distinct variable group:   𝑥,𝑦

Detailed syntax breakdown of Definition df-ltxr
StepHypRef Expression
1 clt 7576 . 2 class <
2 vx . . . . . . 7 setvar 𝑥
32cv 1289 . . . . . 6 class 𝑥
4 cr 7403 . . . . . 6 class
53, 4wcel 1439 . . . . 5 wff 𝑥 ∈ ℝ
6 vy . . . . . . 7 setvar 𝑦
76cv 1289 . . . . . 6 class 𝑦
87, 4wcel 1439 . . . . 5 wff 𝑦 ∈ ℝ
9 cltrr 7408 . . . . . 6 class <
103, 7, 9wbr 3851 . . . . 5 wff 𝑥 < 𝑦
115, 8, 10w3a 925 . . . 4 wff (𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ ∧ 𝑥 < 𝑦)
1211, 2, 6copab 3904 . . 3 class {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ ∧ 𝑥 < 𝑦)}
13 cmnf 7574 . . . . . . 7 class -∞
1413csn 3450 . . . . . 6 class {-∞}
154, 14cun 2998 . . . . 5 class (ℝ ∪ {-∞})
16 cpnf 7573 . . . . . 6 class +∞
1716csn 3450 . . . . 5 class {+∞}
1815, 17cxp 4449 . . . 4 class ((ℝ ∪ {-∞}) × {+∞})
1914, 4cxp 4449 . . . 4 class ({-∞} × ℝ)
2018, 19cun 2998 . . 3 class (((ℝ ∪ {-∞}) × {+∞}) ∪ ({-∞} × ℝ))
2112, 20cun 2998 . 2 class ({⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ ∧ 𝑥 < 𝑦)} ∪ (((ℝ ∪ {-∞}) × {+∞}) ∪ ({-∞} × ℝ)))
221, 21wceq 1290 1 wff < = ({⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ ℝ ∧ 𝑦 ∈ ℝ ∧ 𝑥 < 𝑦)} ∪ (((ℝ ∪ {-∞}) × {+∞}) ∪ ({-∞} × ℝ)))
 Colors of variables: wff set class This definition is referenced by:  ltrelxr  7601  ltxrlt  7606  ltxr  9300
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