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Definition df-mnf 7121
Description: Define minus infinity as the power set of plus infinity. Note that the definition is arbitrary, requiring only that -oo be a set not in  RR and different from +oo (see mnfnre 7126). (Contributed by NM, 13-Oct-2005.) (New usage is discouraged.)
Assertion
Ref Expression
df-mnf  |- -oo  =  ~P +oo

Detailed syntax breakdown of Definition df-mnf
StepHypRef Expression
1 cmnf 7116 . 2  class -oo
2 cpnf 7115 . . 3  class +oo
32cpw 3386 . 2  class  ~P +oo
41, 3wceq 1259 1  wff -oo  =  ~P +oo
Colors of variables: wff set class
This definition is referenced by:  mnfnre  7126  mnfxr  8794  pnfnemnf  8797
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