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Definition df-mnf 9115
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 9120 and pnfnemnf 10709). (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 9110 . 2  class  -oo
2 cpnf 9109 . . 3  class  +oo
32cpw 3791 . 2  class  ~P  +oo
41, 3wceq 1652 1  wff  -oo  =  ~P  +oo
Colors of variables: wff set class
This definition is referenced by:  mnfnre  9120  mnfxr  10706  pnfnemnf  10709
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