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Mirrors > Home > MPE Home > Th. List > pnfxr | Structured version Visualization version GIF version |
Description: Plus infinity belongs to the set of extended reals. (Contributed by NM, 13-Oct-2005.) (Proof shortened by Anthony Hart, 29-Aug-2011.) |
Ref | Expression |
---|---|
pnfxr | ⊢ +∞ ∈ ℝ* |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssun2 4103 | . . 3 ⊢ {+∞, -∞} ⊆ (ℝ ∪ {+∞, -∞}) | |
2 | pnfex 10959 | . . . 4 ⊢ +∞ ∈ V | |
3 | 2 | prid1 4695 | . . 3 ⊢ +∞ ∈ {+∞, -∞} |
4 | 1, 3 | sselii 3914 | . 2 ⊢ +∞ ∈ (ℝ ∪ {+∞, -∞}) |
5 | df-xr 10944 | . 2 ⊢ ℝ* = (ℝ ∪ {+∞, -∞}) | |
6 | 4, 5 | eleqtrri 2838 | 1 ⊢ +∞ ∈ ℝ* |
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