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Definition df-mnf 7504
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 7509). (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 7499 . 2  class -oo
2 cpnf 7498 . . 3  class +oo
32cpw 3425 . 2  class  ~P +oo
41, 3wceq 1289 1  wff -oo  =  ~P +oo
Colors of variables: wff set class
This definition is referenced by:  mnfnre  7509  pnfnemnf  7521  mnfxr  7523
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