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Type | Label | Description |
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Statement | ||
Definition | df-log 26301 | Define the natural logarithm function on complex numbers. It is defined as the principal value, that is, the inverse of the exponential whose imaginary part lies in the interval (-pi, pi]. See http://en.wikipedia.org/wiki/Natural_logarithm and https://en.wikipedia.org/wiki/Complex_logarithm. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ log = ◡(exp ↾ (◡ℑ “ (-π(,]π))) | ||
Definition | df-cxp 26302* | Define the power function on complex numbers. Note that the value of this function when 𝑥 = 0 and (ℜ‘𝑦) ≤ 0, 𝑦 ≠ 0 should properly be undefined, but defining it by convention this way simplifies the domain. (Contributed by Mario Carneiro, 2-Aug-2014.) |
⊢ ↑𝑐 = (𝑥 ∈ ℂ, 𝑦 ∈ ℂ ↦ if(𝑥 = 0, if(𝑦 = 0, 1, 0), (exp‘(𝑦 · (log‘𝑥))))) | ||
Theorem | logrn 26303 | The range of the natural logarithm function, also the principal domain of the exponential function. This allows to write the longer class expression as simply ran log. (Contributed by Paul Chapman, 21-Apr-2008.) (Revised by Mario Carneiro, 13-May-2014.) |
⊢ ran log = (◡ℑ “ (-π(,]π)) | ||
Theorem | ellogrn 26304 | Write out the property 𝐴 ∈ ran log explicitly. (Contributed by Mario Carneiro, 1-Apr-2015.) |
⊢ (𝐴 ∈ ran log ↔ (𝐴 ∈ ℂ ∧ -π < (ℑ‘𝐴) ∧ (ℑ‘𝐴) ≤ π)) | ||
Theorem | dflog2 26305 | The natural logarithm function in terms of the exponential function restricted to its principal domain. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ log = ◡(exp ↾ ran log) | ||
Theorem | relogrn 26306 | The range of the natural logarithm function includes the real numbers. (Contributed by Paul Chapman, 21-Apr-2008.) (Proof shortened by Mario Carneiro, 1-Apr-2015.) |
⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ran log) | ||
Theorem | logrncn 26307 | The range of the natural logarithm function is a subset of the complex numbers. (Contributed by Mario Carneiro, 13-May-2014.) |
⊢ (𝐴 ∈ ran log → 𝐴 ∈ ℂ) | ||
Theorem | eff1o2 26308 | The exponential function restricted to its principal domain maps one-to-one onto the nonzero complex numbers. (Contributed by Paul Chapman, 21-Apr-2008.) (Revised by Mario Carneiro, 13-May-2014.) |
⊢ (exp ↾ ran log):ran log–1-1-onto→(ℂ ∖ {0}) | ||
Theorem | logf1o 26309 | The natural logarithm function maps the nonzero complex numbers one-to-one onto its range. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ log:(ℂ ∖ {0})–1-1-onto→ran log | ||
Theorem | dfrelog 26310 | The natural logarithm function on the positive reals in terms of the real exponential function. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ (log ↾ ℝ+) = ◡(exp ↾ ℝ) | ||
Theorem | relogf1o 26311 | The natural logarithm function maps the positive reals one-to-one onto the real numbers. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ (log ↾ ℝ+):ℝ+–1-1-onto→ℝ | ||
Theorem | logrncl 26312 | Closure of the natural logarithm function. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (log‘𝐴) ∈ ran log) | ||
Theorem | logcl 26313 | Closure of the natural logarithm function. (Contributed by NM, 21-Apr-2008.) (Revised by Mario Carneiro, 23-Sep-2014.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (log‘𝐴) ∈ ℂ) | ||
Theorem | logimcl 26314 | Closure of the imaginary part of the logarithm function. (Contributed by Mario Carneiro, 23-Sep-2014.) (Revised by Mario Carneiro, 1-Apr-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (-π < (ℑ‘(log‘𝐴)) ∧ (ℑ‘(log‘𝐴)) ≤ π)) | ||
Theorem | logcld 26315 | The logarithm of a nonzero complex number is a complex number. Deduction form of logcl 26313. (Contributed by David Moews, 28-Feb-2017.) |
⊢ (𝜑 → 𝑋 ∈ ℂ) & ⊢ (𝜑 → 𝑋 ≠ 0) ⇒ ⊢ (𝜑 → (log‘𝑋) ∈ ℂ) | ||
Theorem | logimcld 26316 | The imaginary part of the logarithm is in (-π(,]π). Deduction form of logimcl 26314. Compare logimclad 26317. (Contributed by David Moews, 28-Feb-2017.) |
⊢ (𝜑 → 𝑋 ∈ ℂ) & ⊢ (𝜑 → 𝑋 ≠ 0) ⇒ ⊢ (𝜑 → (-π < (ℑ‘(log‘𝑋)) ∧ (ℑ‘(log‘𝑋)) ≤ π)) | ||
Theorem | logimclad 26317 | The imaginary part of the logarithm is in (-π(,]π). Alternate form of logimcld 26316. (Contributed by David Moews, 28-Feb-2017.) |
⊢ (𝜑 → 𝑋 ∈ ℂ) & ⊢ (𝜑 → 𝑋 ≠ 0) ⇒ ⊢ (𝜑 → (ℑ‘(log‘𝑋)) ∈ (-π(,]π)) | ||
Theorem | abslogimle 26318 | The imaginary part of the logarithm function has absolute value less than pi. (Contributed by Mario Carneiro, 3-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (abs‘(ℑ‘(log‘𝐴))) ≤ π) | ||
Theorem | logrnaddcl 26319 | The range of the natural logarithm is closed under addition with reals. (Contributed by Mario Carneiro, 3-Apr-2015.) |
⊢ ((𝐴 ∈ ran log ∧ 𝐵 ∈ ℝ) → (𝐴 + 𝐵) ∈ ran log) | ||
Theorem | relogcl 26320 | Closure of the natural logarithm function on positive reals. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (𝐴 ∈ ℝ+ → (log‘𝐴) ∈ ℝ) | ||
Theorem | eflog 26321 | Relationship between the natural logarithm function and the exponential function. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (exp‘(log‘𝐴)) = 𝐴) | ||
Theorem | logeq0im1 26322 | If the logarithm of a number is 0, the number must be 1. (Contributed by David A. Wheeler, 22-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ (log‘𝐴) = 0) → 𝐴 = 1) | ||
Theorem | logccne0 26323 | The logarithm isn't 0 if its argument isn't 0 or 1. (Contributed by David A. Wheeler, 17-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 𝐴 ≠ 1) → (log‘𝐴) ≠ 0) | ||
Theorem | logne0 26324 | Logarithm of a non-1 positive real number is not zero and thus suitable as a divisor. (Contributed by Stefan O'Rear, 19-Sep-2014.) (Proof shortened by AV, 14-Jun-2020.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐴 ≠ 1) → (log‘𝐴) ≠ 0) | ||
Theorem | reeflog 26325 | Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (𝐴 ∈ ℝ+ → (exp‘(log‘𝐴)) = 𝐴) | ||
Theorem | logef 26326 | Relationship between the natural logarithm function and the exponential function. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ (𝐴 ∈ ran log → (log‘(exp‘𝐴)) = 𝐴) | ||
Theorem | relogef 26327 | Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (𝐴 ∈ ℝ → (log‘(exp‘𝐴)) = 𝐴) | ||
Theorem | logeftb 26328 | Relationship between the natural logarithm function and the exponential function. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 𝐵 ∈ ran log) → ((log‘𝐴) = 𝐵 ↔ (exp‘𝐵) = 𝐴)) | ||
Theorem | relogeftb 26329 | Relationship between the natural logarithm function and the exponential function. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ) → ((log‘𝐴) = 𝐵 ↔ (exp‘𝐵) = 𝐴)) | ||
Theorem | log1 26330 | The natural logarithm of 1. One case of Property 1a of [Cohen] p. 301. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (log‘1) = 0 | ||
Theorem | loge 26331 | The natural logarithm of e. One case of Property 1b of [Cohen] p. 301. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (log‘e) = 1 | ||
Theorem | logneg 26332 | The natural logarithm of a negative real number. (Contributed by Mario Carneiro, 13-May-2014.) (Revised by Mario Carneiro, 3-Apr-2015.) |
⊢ (𝐴 ∈ ℝ+ → (log‘-𝐴) = ((log‘𝐴) + (i · π))) | ||
Theorem | logm1 26333 | The natural logarithm of negative 1. (Contributed by Paul Chapman, 21-Apr-2008.) (Revised by Mario Carneiro, 13-May-2014.) |
⊢ (log‘-1) = (i · π) | ||
Theorem | lognegb 26334 | If a number has imaginary part equal to π, then it is on the negative real axis and vice-versa. (Contributed by Mario Carneiro, 23-Sep-2014.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (-𝐴 ∈ ℝ+ ↔ (ℑ‘(log‘𝐴)) = π)) | ||
Theorem | relogoprlem 26335 | Lemma for relogmul 26336 and relogdiv 26337. Remark of [Cohen] p. 301 ("The proof of Property 3 is quite similar to the proof given for Property 2"). (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (((log‘𝐴) ∈ ℂ ∧ (log‘𝐵) ∈ ℂ) → (exp‘((log‘𝐴)𝐹(log‘𝐵))) = ((exp‘(log‘𝐴))𝐺(exp‘(log‘𝐵)))) & ⊢ (((log‘𝐴) ∈ ℝ ∧ (log‘𝐵) ∈ ℝ) → ((log‘𝐴)𝐹(log‘𝐵)) ∈ ℝ) ⇒ ⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ+) → (log‘(𝐴𝐺𝐵)) = ((log‘𝐴)𝐹(log‘𝐵))) | ||
Theorem | relogmul 26336 | The natural logarithm of the product of two positive real numbers is the sum of natural logarithms. Property 2 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ+) → (log‘(𝐴 · 𝐵)) = ((log‘𝐴) + (log‘𝐵))) | ||
Theorem | relogdiv 26337 | The natural logarithm of the quotient of two positive real numbers is the difference of natural logarithms. Exercise 72(a) and Property 3 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ+) → (log‘(𝐴 / 𝐵)) = ((log‘𝐴) − (log‘𝐵))) | ||
Theorem | explog 26338 | Exponentiation of a nonzero complex number to an integer power. (Contributed by Paul Chapman, 21-Apr-2008.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 𝑁 ∈ ℤ) → (𝐴↑𝑁) = (exp‘(𝑁 · (log‘𝐴)))) | ||
Theorem | reexplog 26339 | Exponentiation of a positive real number to an integer power. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝑁 ∈ ℤ) → (𝐴↑𝑁) = (exp‘(𝑁 · (log‘𝐴)))) | ||
Theorem | relogexp 26340 | The natural logarithm of positive 𝐴 raised to an integer power. Property 4 of [Cohen] p. 301-302, restricted to natural logarithms and integer powers 𝑁. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝑁 ∈ ℤ) → (log‘(𝐴↑𝑁)) = (𝑁 · (log‘𝐴))) | ||
Theorem | relog 26341 | Real part of a logarithm. (Contributed by Mario Carneiro, 15-Sep-2014.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (ℜ‘(log‘𝐴)) = (log‘(abs‘𝐴))) | ||
Theorem | relogiso 26342 | The natural logarithm function on positive reals determines an isomorphism from the positive reals onto the reals. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ (log ↾ ℝ+) Isom < , < (ℝ+, ℝ) | ||
Theorem | reloggim 26343 | The natural logarithm is a group isomorphism from the group of positive reals under multiplication to the group of reals under addition. (Contributed by Mario Carneiro, 21-Jun-2015.) (Revised by Thierry Arnoux, 30-Jun-2019.) |
⊢ 𝑃 = ((mulGrp‘ℂfld) ↾s ℝ+) ⇒ ⊢ (log ↾ ℝ+) ∈ (𝑃 GrpIso ℝfld) | ||
Theorem | logltb 26344 | The natural logarithm function on positive reals is strictly monotonic. (Contributed by Steve Rodriguez, 25-Nov-2007.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ+) → (𝐴 < 𝐵 ↔ (log‘𝐴) < (log‘𝐵))) | ||
Theorem | logfac 26345* | The logarithm of a factorial can be expressed as a finite sum of logs. (Contributed by Mario Carneiro, 17-Apr-2015.) |
⊢ (𝑁 ∈ ℕ0 → (log‘(!‘𝑁)) = Σ𝑘 ∈ (1...𝑁)(log‘𝑘)) | ||
Theorem | eflogeq 26346* | Solve an equation involving an exponential. (Contributed by Mario Carneiro, 23-Apr-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐵 ≠ 0) → ((exp‘𝐴) = 𝐵 ↔ ∃𝑛 ∈ ℤ 𝐴 = ((log‘𝐵) + ((i · (2 · π)) · 𝑛)))) | ||
Theorem | logleb 26347 | Natural logarithm preserves ≤. (Contributed by Stefan O'Rear, 19-Sep-2014.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝐵 ∈ ℝ+) → (𝐴 ≤ 𝐵 ↔ (log‘𝐴) ≤ (log‘𝐵))) | ||
Theorem | rplogcl 26348 | Closure of the logarithm function in the positive reals. (Contributed by Mario Carneiro, 21-Sep-2014.) |
⊢ ((𝐴 ∈ ℝ ∧ 1 < 𝐴) → (log‘𝐴) ∈ ℝ+) | ||
Theorem | logge0 26349 | The logarithm of a number greater than 1 is nonnegative. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ ((𝐴 ∈ ℝ ∧ 1 ≤ 𝐴) → 0 ≤ (log‘𝐴)) | ||
Theorem | logcj 26350 | The natural logarithm distributes under conjugation away from the branch cut. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ (ℑ‘𝐴) ≠ 0) → (log‘(∗‘𝐴)) = (∗‘(log‘𝐴))) | ||
Theorem | efiarg 26351 | The exponential of the "arg" function ℑ ∘ log. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (exp‘(i · (ℑ‘(log‘𝐴)))) = (𝐴 / (abs‘𝐴))) | ||
Theorem | cosargd 26352 | The cosine of the argument is the quotient of the real part and the absolute value. Compare to efiarg 26351. (Contributed by David Moews, 28-Feb-2017.) |
⊢ (𝜑 → 𝑋 ∈ ℂ) & ⊢ (𝜑 → 𝑋 ≠ 0) ⇒ ⊢ (𝜑 → (cos‘(ℑ‘(log‘𝑋))) = ((ℜ‘𝑋) / (abs‘𝑋))) | ||
Theorem | cosarg0d 26353 | The cosine of the argument is zero precisely on the imaginary axis. (Contributed by David Moews, 28-Feb-2017.) |
⊢ (𝜑 → 𝑋 ∈ ℂ) & ⊢ (𝜑 → 𝑋 ≠ 0) ⇒ ⊢ (𝜑 → ((cos‘(ℑ‘(log‘𝑋))) = 0 ↔ (ℜ‘𝑋) = 0)) | ||
Theorem | argregt0 26354 | Closure of the argument of a complex number with positive real part. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 0 < (ℜ‘𝐴)) → (ℑ‘(log‘𝐴)) ∈ (-(π / 2)(,)(π / 2))) | ||
Theorem | argrege0 26355 | Closure of the argument of a complex number with nonnegative real part. (Contributed by Mario Carneiro, 2-Apr-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 0 ≤ (ℜ‘𝐴)) → (ℑ‘(log‘𝐴)) ∈ (-(π / 2)[,](π / 2))) | ||
Theorem | argimgt0 26356 | Closure of the argument of a complex number with positive imaginary part. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 0 < (ℑ‘𝐴)) → (ℑ‘(log‘𝐴)) ∈ (0(,)π)) | ||
Theorem | argimlt0 26357 | Closure of the argument of a complex number with negative imaginary part. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ (ℑ‘𝐴) < 0) → (ℑ‘(log‘𝐴)) ∈ (-π(,)0)) | ||
Theorem | logimul 26358 | Multiplying a number by i increases the logarithm of the number by iπ / 2. (Contributed by Mario Carneiro, 4-Apr-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 0 ≤ (ℜ‘𝐴)) → (log‘(i · 𝐴)) = ((log‘𝐴) + (i · (π / 2)))) | ||
Theorem | logneg2 26359 | The logarithm of the negative of a number with positive imaginary part is i · π less than the original. (Compare logneg 26332.) (Contributed by Mario Carneiro, 3-Apr-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ 0 < (ℑ‘𝐴)) → (log‘-𝐴) = ((log‘𝐴) − (i · π))) | ||
Theorem | logmul2 26360 | Generalization of relogmul 26336 to a complex left argument. (Contributed by Mario Carneiro, 9-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 𝐵 ∈ ℝ+) → (log‘(𝐴 · 𝐵)) = ((log‘𝐴) + (log‘𝐵))) | ||
Theorem | logdiv2 26361 | Generalization of relogdiv 26337 to a complex left argument. (Contributed by Mario Carneiro, 8-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0 ∧ 𝐵 ∈ ℝ+) → (log‘(𝐴 / 𝐵)) = ((log‘𝐴) − (log‘𝐵))) | ||
Theorem | abslogle 26362 | Bound on the magnitude of the complex logarithm function. (Contributed by Mario Carneiro, 3-Jul-2017.) |
⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (abs‘(log‘𝐴)) ≤ ((abs‘(log‘(abs‘𝐴))) + π)) | ||
Theorem | tanarg 26363 | The basic relation between the "arg" function ℑ ∘ log and the arctangent. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ ((𝐴 ∈ ℂ ∧ (ℜ‘𝐴) ≠ 0) → (tan‘(ℑ‘(log‘𝐴))) = ((ℑ‘𝐴) / (ℜ‘𝐴))) | ||
Theorem | logdivlti 26364 | The log𝑥 / 𝑥 function is strictly decreasing on the reals greater than e. (Contributed by Mario Carneiro, 14-Mar-2014.) |
⊢ (((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ e ≤ 𝐴) ∧ 𝐴 < 𝐵) → ((log‘𝐵) / 𝐵) < ((log‘𝐴) / 𝐴)) | ||
Theorem | logdivlt 26365 | The log𝑥 / 𝑥 function is strictly decreasing on the reals greater than e. (Contributed by Mario Carneiro, 14-Mar-2014.) |
⊢ (((𝐴 ∈ ℝ ∧ e ≤ 𝐴) ∧ (𝐵 ∈ ℝ ∧ e ≤ 𝐵)) → (𝐴 < 𝐵 ↔ ((log‘𝐵) / 𝐵) < ((log‘𝐴) / 𝐴))) | ||
Theorem | logdivle 26366 | The log𝑥 / 𝑥 function is strictly decreasing on the reals greater than e. (Contributed by Mario Carneiro, 3-May-2016.) |
⊢ (((𝐴 ∈ ℝ ∧ e ≤ 𝐴) ∧ (𝐵 ∈ ℝ ∧ e ≤ 𝐵)) → (𝐴 ≤ 𝐵 ↔ ((log‘𝐵) / 𝐵) ≤ ((log‘𝐴) / 𝐴))) | ||
Theorem | relogcld 26367 | Closure of the natural logarithm function. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ+) ⇒ ⊢ (𝜑 → (log‘𝐴) ∈ ℝ) | ||
Theorem | reeflogd 26368 | Relationship between the natural logarithm function and the exponential function. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ+) ⇒ ⊢ (𝜑 → (exp‘(log‘𝐴)) = 𝐴) | ||
Theorem | relogmuld 26369 | The natural logarithm of the product of two positive real numbers is the sum of natural logarithms. Property 2 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ+) & ⊢ (𝜑 → 𝐵 ∈ ℝ+) ⇒ ⊢ (𝜑 → (log‘(𝐴 · 𝐵)) = ((log‘𝐴) + (log‘𝐵))) | ||
Theorem | relogdivd 26370 | The natural logarithm of the quotient of two positive real numbers is the difference of natural logarithms. Exercise 72(a) and Property 3 of [Cohen] p. 301, restricted to natural logarithms. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ+) & ⊢ (𝜑 → 𝐵 ∈ ℝ+) ⇒ ⊢ (𝜑 → (log‘(𝐴 / 𝐵)) = ((log‘𝐴) − (log‘𝐵))) | ||
Theorem | logled 26371 | Natural logarithm preserves ≤. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ+) & ⊢ (𝜑 → 𝐵 ∈ ℝ+) ⇒ ⊢ (𝜑 → (𝐴 ≤ 𝐵 ↔ (log‘𝐴) ≤ (log‘𝐵))) | ||
Theorem | relogefd 26372 | Relationship between the natural logarithm function and the exponential function. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ) ⇒ ⊢ (𝜑 → (log‘(exp‘𝐴)) = 𝐴) | ||
Theorem | rplogcld 26373 | Closure of the logarithm function in the positive reals. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 1 < 𝐴) ⇒ ⊢ (𝜑 → (log‘𝐴) ∈ ℝ+) | ||
Theorem | logge0d 26374 | The logarithm of a number greater than 1 is nonnegative. (Contributed by Mario Carneiro, 29-May-2016.) |
⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 1 ≤ 𝐴) ⇒ ⊢ (𝜑 → 0 ≤ (log‘𝐴)) | ||
Theorem | logge0b 26375 | The logarithm of a number is nonnegative iff the number is greater than or equal to 1. (Contributed by AV, 30-May-2020.) |
⊢ (𝐴 ∈ ℝ+ → (0 ≤ (log‘𝐴) ↔ 1 ≤ 𝐴)) | ||
Theorem | loggt0b 26376 | The logarithm of a number is positive iff the number is greater than 1. (Contributed by AV, 30-May-2020.) |
⊢ (𝐴 ∈ ℝ+ → (0 < (log‘𝐴) ↔ 1 < 𝐴)) | ||
Theorem | logle1b 26377 | The logarithm of a number is less than or equal to 1 iff the number is less than or equal to Euler's constant. (Contributed by AV, 30-May-2020.) |
⊢ (𝐴 ∈ ℝ+ → ((log‘𝐴) ≤ 1 ↔ 𝐴 ≤ e)) | ||
Theorem | loglt1b 26378 | The logarithm of a number is less than 1 iff the number is less than Euler's constant. (Contributed by AV, 30-May-2020.) |
⊢ (𝐴 ∈ ℝ+ → ((log‘𝐴) < 1 ↔ 𝐴 < e)) | ||
Theorem | divlogrlim 26379 | The inverse logarithm function converges to zero. (Contributed by Mario Carneiro, 30-May-2016.) |
⊢ (𝑥 ∈ (1(,)+∞) ↦ (1 / (log‘𝑥))) ⇝𝑟 0 | ||
Theorem | logno1 26380 | The logarithm function is not eventually bounded. (Contributed by Mario Carneiro, 30-Apr-2016.) (Proof shortened by Mario Carneiro, 30-May-2016.) |
⊢ ¬ (𝑥 ∈ ℝ+ ↦ (log‘𝑥)) ∈ 𝑂(1) | ||
Theorem | dvrelog 26381 | The derivative of the real logarithm function. (Contributed by Mario Carneiro, 24-Feb-2015.) |
⊢ (ℝ D (log ↾ ℝ+)) = (𝑥 ∈ ℝ+ ↦ (1 / 𝑥)) | ||
Theorem | relogcn 26382 | The real logarithm function is continuous. (Contributed by Mario Carneiro, 17-Feb-2015.) |
⊢ (log ↾ ℝ+) ∈ (ℝ+–cn→ℝ) | ||
Theorem | ellogdm 26383 | Elementhood in the "continuous domain" of the complex logarithm. (Contributed by Mario Carneiro, 18-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (𝐴 ∈ 𝐷 ↔ (𝐴 ∈ ℂ ∧ (𝐴 ∈ ℝ → 𝐴 ∈ ℝ+))) | ||
Theorem | logdmn0 26384 | A number in the continuous domain of log is nonzero. (Contributed by Mario Carneiro, 18-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (𝐴 ∈ 𝐷 → 𝐴 ≠ 0) | ||
Theorem | logdmnrp 26385 | A number in the continuous domain of log is not a strictly negative number. (Contributed by Mario Carneiro, 18-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (𝐴 ∈ 𝐷 → ¬ -𝐴 ∈ ℝ+) | ||
Theorem | logdmss 26386 | The continuity domain of log is a subset of the regular domain of log. (Contributed by Mario Carneiro, 1-Mar-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ 𝐷 ⊆ (ℂ ∖ {0}) | ||
Theorem | logcnlem2 26387 | Lemma for logcn 26391. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) & ⊢ 𝑆 = if(𝐴 ∈ ℝ+, 𝐴, (abs‘(ℑ‘𝐴))) & ⊢ 𝑇 = ((abs‘𝐴) · (𝑅 / (1 + 𝑅))) & ⊢ (𝜑 → 𝐴 ∈ 𝐷) & ⊢ (𝜑 → 𝑅 ∈ ℝ+) ⇒ ⊢ (𝜑 → if(𝑆 ≤ 𝑇, 𝑆, 𝑇) ∈ ℝ+) | ||
Theorem | logcnlem3 26388 | Lemma for logcn 26391. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) & ⊢ 𝑆 = if(𝐴 ∈ ℝ+, 𝐴, (abs‘(ℑ‘𝐴))) & ⊢ 𝑇 = ((abs‘𝐴) · (𝑅 / (1 + 𝑅))) & ⊢ (𝜑 → 𝐴 ∈ 𝐷) & ⊢ (𝜑 → 𝑅 ∈ ℝ+) & ⊢ (𝜑 → 𝐵 ∈ 𝐷) & ⊢ (𝜑 → (abs‘(𝐴 − 𝐵)) < if(𝑆 ≤ 𝑇, 𝑆, 𝑇)) ⇒ ⊢ (𝜑 → (-π < ((ℑ‘(log‘𝐵)) − (ℑ‘(log‘𝐴))) ∧ ((ℑ‘(log‘𝐵)) − (ℑ‘(log‘𝐴))) ≤ π)) | ||
Theorem | logcnlem4 26389 | Lemma for logcn 26391. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) & ⊢ 𝑆 = if(𝐴 ∈ ℝ+, 𝐴, (abs‘(ℑ‘𝐴))) & ⊢ 𝑇 = ((abs‘𝐴) · (𝑅 / (1 + 𝑅))) & ⊢ (𝜑 → 𝐴 ∈ 𝐷) & ⊢ (𝜑 → 𝑅 ∈ ℝ+) & ⊢ (𝜑 → 𝐵 ∈ 𝐷) & ⊢ (𝜑 → (abs‘(𝐴 − 𝐵)) < if(𝑆 ≤ 𝑇, 𝑆, 𝑇)) ⇒ ⊢ (𝜑 → (abs‘((ℑ‘(log‘𝐴)) − (ℑ‘(log‘𝐵)))) < 𝑅) | ||
Theorem | logcnlem5 26390* | Lemma for logcn 26391. (Contributed by Mario Carneiro, 18-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (𝑥 ∈ 𝐷 ↦ (ℑ‘(log‘𝑥))) ∈ (𝐷–cn→ℝ) | ||
Theorem | logcn 26391 | The logarithm function is continuous away from the branch cut at negative reals. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (log ↾ 𝐷) ∈ (𝐷–cn→ℂ) | ||
Theorem | dvloglem 26392 | Lemma for dvlog 26395. (Contributed by Mario Carneiro, 24-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (log “ 𝐷) ∈ (TopOpen‘ℂfld) | ||
Theorem | logdmopn 26393 | The "continuous domain" of log is an open set. (Contributed by Mario Carneiro, 7-Apr-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ 𝐷 ∈ (TopOpen‘ℂfld) | ||
Theorem | logf1o2 26394 | The logarithm maps its continuous domain bijectively onto the set of numbers with imaginary part -π < ℑ(𝑧) < π. The negative reals are mapped to the numbers with imaginary part equal to π. (Contributed by Mario Carneiro, 2-May-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (log ↾ 𝐷):𝐷–1-1-onto→(◡ℑ “ (-π(,)π)) | ||
Theorem | dvlog 26395* | The derivative of the complex logarithm function. (Contributed by Mario Carneiro, 25-Feb-2015.) |
⊢ 𝐷 = (ℂ ∖ (-∞(,]0)) ⇒ ⊢ (ℂ D (log ↾ 𝐷)) = (𝑥 ∈ 𝐷 ↦ (1 / 𝑥)) | ||
Theorem | dvlog2lem 26396 | Lemma for dvlog2 26397. (Contributed by Mario Carneiro, 1-Mar-2015.) |
⊢ 𝑆 = (1(ball‘(abs ∘ − ))1) ⇒ ⊢ 𝑆 ⊆ (ℂ ∖ (-∞(,]0)) | ||
Theorem | dvlog2 26397* | The derivative of the complex logarithm function on the open unit ball centered at 1, a sometimes easier region to work with than the ℂ ∖ (-∞, 0] of dvlog 26395. (Contributed by Mario Carneiro, 1-Mar-2015.) |
⊢ 𝑆 = (1(ball‘(abs ∘ − ))1) ⇒ ⊢ (ℂ D (log ↾ 𝑆)) = (𝑥 ∈ 𝑆 ↦ (1 / 𝑥)) | ||
Theorem | advlog 26398 | The antiderivative of the logarithm. (Contributed by Mario Carneiro, 21-May-2016.) |
⊢ (ℝ D (𝑥 ∈ ℝ+ ↦ (𝑥 · ((log‘𝑥) − 1)))) = (𝑥 ∈ ℝ+ ↦ (log‘𝑥)) | ||
Theorem | advlogexp 26399* | The antiderivative of a power of the logarithm. (Set 𝐴 = 1 and multiply by (-1)↑𝑁 · 𝑁! to get the antiderivative of log(𝑥)↑𝑁 itself.) (Contributed by Mario Carneiro, 22-May-2016.) |
⊢ ((𝐴 ∈ ℝ+ ∧ 𝑁 ∈ ℕ0) → (ℝ D (𝑥 ∈ ℝ+ ↦ (𝑥 · Σ𝑘 ∈ (0...𝑁)(((log‘(𝐴 / 𝑥))↑𝑘) / (!‘𝑘))))) = (𝑥 ∈ ℝ+ ↦ (((log‘(𝐴 / 𝑥))↑𝑁) / (!‘𝑁)))) | ||
Theorem | efopnlem1 26400 | Lemma for efopn 26402. (Contributed by Mario Carneiro, 23-Apr-2015.) (Revised by Mario Carneiro, 8-Sep-2015.) |
⊢ (((𝑅 ∈ ℝ+ ∧ 𝑅 < π) ∧ 𝐴 ∈ (0(ball‘(abs ∘ − ))𝑅)) → (abs‘(ℑ‘𝐴)) < π) |
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