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Definition df-relog 13007
 Description: Define the natural logarithm function. Defining the logarithm on complex numbers is similar to square root - there are ways to define it but they tend to make use of excluded middle. Therefore, we merely define logarithms on positive reals. See http://en.wikipedia.org/wiki/Natural_logarithm and https://en.wikipedia.org/wiki/Complex_logarithm. (Contributed by Jim Kingdon, 14-May-2024.)
Assertion
Ref Expression
df-relog log = (exp ↾ ℝ)

Detailed syntax breakdown of Definition df-relog
StepHypRef Expression
1 clog 13005 . 2 class log
2 ce 11405 . . . 4 class exp
3 cr 7663 . . . 4 class
42, 3cres 4550 . . 3 class (exp ↾ ℝ)
54ccnv 4547 . 2 class (exp ↾ ℝ)
61, 5wceq 1332 1 wff log = (exp ↾ ℝ)
 Colors of variables: wff set class This definition is referenced by:  dfrelog  13009  reeflog  13012
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