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Definition df-mnf 9933
Description: Define minus infinity as the power set of plus infinity. Note that the definition is arbitrary, requiring only that -∞ be a set not in and different from +∞ (see mnfnre 9938 and pnfnemnf 11788). (Contributed by NM, 13-Oct-2005.) (New usage is discouraged.)
Assertion
Ref Expression
df-mnf -∞ = 𝒫 +∞

Detailed syntax breakdown of Definition df-mnf
StepHypRef Expression
1 cmnf 9928 . 2 class -∞
2 cpnf 9927 . . 3 class +∞
32cpw 4107 . 2 class 𝒫 +∞
41, 3wceq 1474 1 wff -∞ = 𝒫 +∞
Colors of variables: wff setvar class
This definition is referenced by:  mnfnre  9938  mnfxr  11785  pnfnemnf  11788
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