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Theorem List for Intuitionistic Logic Explorer - 10801-10900   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremabsrpclap 10801 The absolute value of a number apart from zero is a positive real. (Contributed by Jim Kingdon, 11-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐴 # 0) → (abs‘𝐴) ∈ ℝ+)
 
Theoremabs00ap 10802 The absolute value of a number is apart from zero iff the number is apart from zero. (Contributed by Jim Kingdon, 11-Aug-2021.)
(𝐴 ∈ ℂ → ((abs‘𝐴) # 0 ↔ 𝐴 # 0))
 
Theoremabsext 10803 Strong extensionality for absolute value. (Contributed by Jim Kingdon, 12-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((abs‘𝐴) # (abs‘𝐵) → 𝐴 # 𝐵))
 
Theoremabs00 10804 The absolute value of a number is zero iff the number is zero. Also see abs00ap 10802 which is similar but for apartness. Proposition 10-3.7(c) of [Gleason] p. 133. (Contributed by NM, 26-Sep-2005.) (Proof shortened by Mario Carneiro, 29-May-2016.)
(𝐴 ∈ ℂ → ((abs‘𝐴) = 0 ↔ 𝐴 = 0))
 
Theoremabs00ad 10805 A complex number is zero iff its absolute value is zero. Deduction form of abs00 10804. (Contributed by David Moews, 28-Feb-2017.)
(𝜑𝐴 ∈ ℂ)       (𝜑 → ((abs‘𝐴) = 0 ↔ 𝐴 = 0))
 
Theoremabs00bd 10806 If a complex number is zero, its absolute value is zero. (Contributed by David Moews, 28-Feb-2017.)
(𝜑𝐴 = 0)       (𝜑 → (abs‘𝐴) = 0)
 
Theoremabsreimsq 10807 Square of the absolute value of a number that has been decomposed into real and imaginary parts. (Contributed by NM, 1-Feb-2007.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((abs‘(𝐴 + (i · 𝐵)))↑2) = ((𝐴↑2) + (𝐵↑2)))
 
Theoremabsreim 10808 Absolute value of a number that has been decomposed into real and imaginary parts. (Contributed by NM, 14-Jan-2006.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → (abs‘(𝐴 + (i · 𝐵))) = (√‘((𝐴↑2) + (𝐵↑2))))
 
Theoremabsmul 10809 Absolute value distributes over multiplication. Proposition 10-3.7(f) of [Gleason] p. 133. (Contributed by NM, 11-Oct-1999.) (Revised by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘(𝐴 · 𝐵)) = ((abs‘𝐴) · (abs‘𝐵)))
 
Theoremabsdivap 10810 Absolute value distributes over division. (Contributed by Jim Kingdon, 11-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐵 # 0) → (abs‘(𝐴 / 𝐵)) = ((abs‘𝐴) / (abs‘𝐵)))
 
Theoremabsid 10811 A nonnegative number is its own absolute value. (Contributed by NM, 11-Oct-1999.) (Revised by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℝ ∧ 0 ≤ 𝐴) → (abs‘𝐴) = 𝐴)
 
Theoremabs1 10812 The absolute value of 1. Common special case. (Contributed by David A. Wheeler, 16-Jul-2016.)
(abs‘1) = 1
 
Theoremabsnid 10813 A negative number is the negative of its own absolute value. (Contributed by NM, 27-Feb-2005.)
((𝐴 ∈ ℝ ∧ 𝐴 ≤ 0) → (abs‘𝐴) = -𝐴)
 
Theoremleabs 10814 A real number is less than or equal to its absolute value. (Contributed by NM, 27-Feb-2005.)
(𝐴 ∈ ℝ → 𝐴 ≤ (abs‘𝐴))
 
Theoremqabsor 10815 The absolute value of a rational number is either that number or its negative. (Contributed by Jim Kingdon, 8-Nov-2021.)
(𝐴 ∈ ℚ → ((abs‘𝐴) = 𝐴 ∨ (abs‘𝐴) = -𝐴))
 
Theoremqabsord 10816 The absolute value of a rational number is either that number or its negative. (Contributed by Jim Kingdon, 8-Nov-2021.)
(𝜑𝐴 ∈ ℚ)       (𝜑 → ((abs‘𝐴) = 𝐴 ∨ (abs‘𝐴) = -𝐴))
 
Theoremabsre 10817 Absolute value of a real number. (Contributed by NM, 17-Mar-2005.)
(𝐴 ∈ ℝ → (abs‘𝐴) = (√‘(𝐴↑2)))
 
Theoremabsresq 10818 Square of the absolute value of a real number. (Contributed by NM, 16-Jan-2006.)
(𝐴 ∈ ℝ → ((abs‘𝐴)↑2) = (𝐴↑2))
 
Theoremabsexp 10819 Absolute value of positive integer exponentiation. (Contributed by NM, 5-Jan-2006.)
((𝐴 ∈ ℂ ∧ 𝑁 ∈ ℕ0) → (abs‘(𝐴𝑁)) = ((abs‘𝐴)↑𝑁))
 
Theoremabsexpzap 10820 Absolute value of integer exponentiation. (Contributed by Jim Kingdon, 11-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐴 # 0 ∧ 𝑁 ∈ ℤ) → (abs‘(𝐴𝑁)) = ((abs‘𝐴)↑𝑁))
 
Theoremabssq 10821 Square can be moved in and out of absolute value. (Contributed by Scott Fenton, 18-Apr-2014.) (Proof shortened by Mario Carneiro, 29-May-2016.)
(𝐴 ∈ ℂ → ((abs‘𝐴)↑2) = (abs‘(𝐴↑2)))
 
Theoremsqabs 10822 The squares of two reals are equal iff their absolute values are equal. (Contributed by NM, 6-Mar-2009.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((𝐴↑2) = (𝐵↑2) ↔ (abs‘𝐴) = (abs‘𝐵)))
 
Theoremabsrele 10823 The absolute value of a complex number is greater than or equal to the absolute value of its real part. (Contributed by NM, 1-Apr-2005.)
(𝐴 ∈ ℂ → (abs‘(ℜ‘𝐴)) ≤ (abs‘𝐴))
 
Theoremabsimle 10824 The absolute value of a complex number is greater than or equal to the absolute value of its imaginary part. (Contributed by NM, 17-Mar-2005.) (Proof shortened by Mario Carneiro, 29-May-2016.)
(𝐴 ∈ ℂ → (abs‘(ℑ‘𝐴)) ≤ (abs‘𝐴))
 
Theoremnn0abscl 10825 The absolute value of an integer is a nonnegative integer. (Contributed by NM, 27-Feb-2005.)
(𝐴 ∈ ℤ → (abs‘𝐴) ∈ ℕ0)
 
Theoremzabscl 10826 The absolute value of an integer is an integer. (Contributed by Stefan O'Rear, 24-Sep-2014.)
(𝐴 ∈ ℤ → (abs‘𝐴) ∈ ℤ)
 
Theoremltabs 10827 A number which is less than its absolute value is negative. (Contributed by Jim Kingdon, 12-Aug-2021.)
((𝐴 ∈ ℝ ∧ 𝐴 < (abs‘𝐴)) → 𝐴 < 0)
 
Theoremabslt 10828 Absolute value and 'less than' relation. (Contributed by NM, 6-Apr-2005.) (Revised by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((abs‘𝐴) < 𝐵 ↔ (-𝐵 < 𝐴𝐴 < 𝐵)))
 
Theoremabsle 10829 Absolute value and 'less than or equal to' relation. (Contributed by NM, 6-Apr-2005.) (Revised by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → ((abs‘𝐴) ≤ 𝐵 ↔ (-𝐵𝐴𝐴𝐵)))
 
Theoremabssubap0 10830 If the absolute value of a complex number is less than a real, its difference from the real is apart from zero. (Contributed by Jim Kingdon, 12-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℝ ∧ (abs‘𝐴) < 𝐵) → (𝐵𝐴) # 0)
 
Theoremabssubne0 10831 If the absolute value of a complex number is less than a real, its difference from the real is nonzero. See also abssubap0 10830 which is the same with not equal changed to apart. (Contributed by NM, 2-Nov-2007.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℝ ∧ (abs‘𝐴) < 𝐵) → (𝐵𝐴) ≠ 0)
 
Theoremabsdiflt 10832 The absolute value of a difference and 'less than' relation. (Contributed by Paul Chapman, 18-Sep-2007.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → ((abs‘(𝐴𝐵)) < 𝐶 ↔ ((𝐵𝐶) < 𝐴𝐴 < (𝐵 + 𝐶))))
 
Theoremabsdifle 10833 The absolute value of a difference and 'less than or equal to' relation. (Contributed by Paul Chapman, 18-Sep-2007.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → ((abs‘(𝐴𝐵)) ≤ 𝐶 ↔ ((𝐵𝐶) ≤ 𝐴𝐴 ≤ (𝐵 + 𝐶))))
 
Theoremelicc4abs 10834 Membership in a symmetric closed real interval. (Contributed by Stefan O'Rear, 16-Nov-2014.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐶 ∈ ℝ) → (𝐶 ∈ ((𝐴𝐵)[,](𝐴 + 𝐵)) ↔ (abs‘(𝐶𝐴)) ≤ 𝐵))
 
Theoremlenegsq 10835 Comparison to a nonnegative number based on comparison to squares. (Contributed by NM, 16-Jan-2006.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 0 ≤ 𝐵) → ((𝐴𝐵 ∧ -𝐴𝐵) ↔ (𝐴↑2) ≤ (𝐵↑2)))
 
Theoremreleabs 10836 The real part of a number is less than or equal to its absolute value. Proposition 10-3.7(d) of [Gleason] p. 133. (Contributed by NM, 1-Apr-2005.)
(𝐴 ∈ ℂ → (ℜ‘𝐴) ≤ (abs‘𝐴))
 
Theoremrecvalap 10837 Reciprocal expressed with a real denominator. (Contributed by Jim Kingdon, 13-Aug-2021.)
((𝐴 ∈ ℂ ∧ 𝐴 # 0) → (1 / 𝐴) = ((∗‘𝐴) / ((abs‘𝐴)↑2)))
 
Theoremabsidm 10838 The absolute value function is idempotent. (Contributed by NM, 20-Nov-2004.)
(𝐴 ∈ ℂ → (abs‘(abs‘𝐴)) = (abs‘𝐴))
 
Theoremabsgt0ap 10839 The absolute value of a number apart from zero is positive. (Contributed by Jim Kingdon, 13-Aug-2021.)
(𝐴 ∈ ℂ → (𝐴 # 0 ↔ 0 < (abs‘𝐴)))
 
Theoremnnabscl 10840 The absolute value of a nonzero integer is a positive integer. (Contributed by Paul Chapman, 21-Mar-2011.) (Proof shortened by Andrew Salmon, 25-May-2011.)
((𝑁 ∈ ℤ ∧ 𝑁 ≠ 0) → (abs‘𝑁) ∈ ℕ)
 
Theoremabssub 10841 Swapping order of subtraction doesn't change the absolute value. (Contributed by NM, 1-Oct-1999.) (Proof shortened by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘(𝐴𝐵)) = (abs‘(𝐵𝐴)))
 
Theoremabssubge0 10842 Absolute value of a nonnegative difference. (Contributed by NM, 14-Feb-2008.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐴𝐵) → (abs‘(𝐵𝐴)) = (𝐵𝐴))
 
Theoremabssuble0 10843 Absolute value of a nonpositive difference. (Contributed by FL, 3-Jan-2008.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐴𝐵) → (abs‘(𝐴𝐵)) = (𝐵𝐴))
 
Theoremabstri 10844 Triangle inequality for absolute value. Proposition 10-3.7(h) of [Gleason] p. 133. (Contributed by NM, 7-Mar-2005.) (Proof shortened by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘(𝐴 + 𝐵)) ≤ ((abs‘𝐴) + (abs‘𝐵)))
 
Theoremabs3dif 10845 Absolute value of differences around common element. (Contributed by FL, 9-Oct-2006.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ ∧ 𝐶 ∈ ℂ) → (abs‘(𝐴𝐵)) ≤ ((abs‘(𝐴𝐶)) + (abs‘(𝐶𝐵))))
 
Theoremabs2dif 10846 Difference of absolute values. (Contributed by Paul Chapman, 7-Sep-2007.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((abs‘𝐴) − (abs‘𝐵)) ≤ (abs‘(𝐴𝐵)))
 
Theoremabs2dif2 10847 Difference of absolute values. (Contributed by Mario Carneiro, 14-Apr-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘(𝐴𝐵)) ≤ ((abs‘𝐴) + (abs‘𝐵)))
 
Theoremabs2difabs 10848 Absolute value of difference of absolute values. (Contributed by Paul Chapman, 7-Sep-2007.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘((abs‘𝐴) − (abs‘𝐵))) ≤ (abs‘(𝐴𝐵)))
 
Theoremrecan 10849* Cancellation law involving the real part of a complex number. (Contributed by NM, 12-May-2005.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (∀𝑥 ∈ ℂ (ℜ‘(𝑥 · 𝐴)) = (ℜ‘(𝑥 · 𝐵)) ↔ 𝐴 = 𝐵))
 
Theoremabsf 10850 Mapping domain and codomain of the absolute value function. (Contributed by NM, 30-Aug-2007.) (Revised by Mario Carneiro, 7-Nov-2013.)
abs:ℂ⟶ℝ
 
Theoremabs3lem 10851 Lemma involving absolute value of differences. (Contributed by NM, 2-Oct-1999.)
(((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) ∧ (𝐶 ∈ ℂ ∧ 𝐷 ∈ ℝ)) → (((abs‘(𝐴𝐶)) < (𝐷 / 2) ∧ (abs‘(𝐶𝐵)) < (𝐷 / 2)) → (abs‘(𝐴𝐵)) < 𝐷))
 
Theoremfzomaxdiflem 10852 Lemma for fzomaxdif 10853. (Contributed by Stefan O'Rear, 6-Sep-2015.)
(((𝐴 ∈ (𝐶..^𝐷) ∧ 𝐵 ∈ (𝐶..^𝐷)) ∧ 𝐴𝐵) → (abs‘(𝐵𝐴)) ∈ (0..^(𝐷𝐶)))
 
Theoremfzomaxdif 10853 A bound on the separation of two points in a half-open range. (Contributed by Stefan O'Rear, 6-Sep-2015.)
((𝐴 ∈ (𝐶..^𝐷) ∧ 𝐵 ∈ (𝐶..^𝐷)) → (abs‘(𝐴𝐵)) ∈ (0..^(𝐷𝐶)))
 
Theoremcau3lem 10854* Lemma for cau3 10855. (Contributed by Mario Carneiro, 15-Feb-2014.) (Revised by Mario Carneiro, 1-May-2014.)
𝑍 ⊆ ℤ    &   (𝜏𝜓)    &   ((𝐹𝑘) = (𝐹𝑗) → (𝜓𝜒))    &   ((𝐹𝑘) = (𝐹𝑚) → (𝜓𝜃))    &   ((𝜑𝜒𝜓) → (𝐺‘((𝐹𝑗)𝐷(𝐹𝑘))) = (𝐺‘((𝐹𝑘)𝐷(𝐹𝑗))))    &   ((𝜑𝜃𝜒) → (𝐺‘((𝐹𝑚)𝐷(𝐹𝑗))) = (𝐺‘((𝐹𝑗)𝐷(𝐹𝑚))))    &   ((𝜑 ∧ (𝜓𝜃) ∧ (𝜒𝑥 ∈ ℝ)) → (((𝐺‘((𝐹𝑘)𝐷(𝐹𝑗))) < (𝑥 / 2) ∧ (𝐺‘((𝐹𝑗)𝐷(𝐹𝑚))) < (𝑥 / 2)) → (𝐺‘((𝐹𝑘)𝐷(𝐹𝑚))) < 𝑥))       (𝜑 → (∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)(𝜏 ∧ (𝐺‘((𝐹𝑘)𝐷(𝐹𝑗))) < 𝑥) ↔ ∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)(𝜏 ∧ ∀𝑚 ∈ (ℤ𝑘)(𝐺‘((𝐹𝑘)𝐷(𝐹𝑚))) < 𝑥)))
 
Theoremcau3 10855* Convert between three-quantifier and four-quantifier versions of the Cauchy criterion. (In particular, the four-quantifier version has no occurrence of 𝑗 in the assertion, so it can be used with rexanuz 10728 and friends.) (Contributed by Mario Carneiro, 15-Feb-2014.)
𝑍 = (ℤ𝑀)       (∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)((𝐹𝑘) ∈ ℂ ∧ (abs‘((𝐹𝑘) − (𝐹𝑗))) < 𝑥) ↔ ∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)((𝐹𝑘) ∈ ℂ ∧ ∀𝑚 ∈ (ℤ𝑘)(abs‘((𝐹𝑘) − (𝐹𝑚))) < 𝑥))
 
Theoremcau4 10856* Change the base of a Cauchy criterion. (Contributed by Mario Carneiro, 18-Mar-2014.)
𝑍 = (ℤ𝑀)    &   𝑊 = (ℤ𝑁)       (𝑁𝑍 → (∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)((𝐹𝑘) ∈ ℂ ∧ (abs‘((𝐹𝑘) − (𝐹𝑗))) < 𝑥) ↔ ∀𝑥 ∈ ℝ+𝑗𝑊𝑘 ∈ (ℤ𝑗)((𝐹𝑘) ∈ ℂ ∧ (abs‘((𝐹𝑘) − (𝐹𝑗))) < 𝑥)))
 
Theoremcaubnd2 10857* A Cauchy sequence of complex numbers is eventually bounded. (Contributed by Mario Carneiro, 14-Feb-2014.)
𝑍 = (ℤ𝑀)       (∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)((𝐹𝑘) ∈ ℂ ∧ (abs‘((𝐹𝑘) − (𝐹𝑗))) < 𝑥) → ∃𝑦 ∈ ℝ ∃𝑗𝑍𝑘 ∈ (ℤ𝑗)(abs‘(𝐹𝑘)) < 𝑦)
 
Theoremamgm2 10858 Arithmetic-geometric mean inequality for 𝑛 = 2. (Contributed by Mario Carneiro, 2-Jul-2014.)
(((𝐴 ∈ ℝ ∧ 0 ≤ 𝐴) ∧ (𝐵 ∈ ℝ ∧ 0 ≤ 𝐵)) → (√‘(𝐴 · 𝐵)) ≤ ((𝐴 + 𝐵) / 2))
 
Theoremsqrtthi 10859 Square root theorem. Theorem I.35 of [Apostol] p. 29. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → ((√‘𝐴) · (√‘𝐴)) = 𝐴)
 
Theoremsqrtcli 10860 The square root of a nonnegative real is a real. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (√‘𝐴) ∈ ℝ)
 
Theoremsqrtgt0i 10861 The square root of a positive real is positive. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ       (0 < 𝐴 → 0 < (√‘𝐴))
 
Theoremsqrtmsqi 10862 Square root of square. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (√‘(𝐴 · 𝐴)) = 𝐴)
 
Theoremsqrtsqi 10863 Square root of square. (Contributed by NM, 11-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (√‘(𝐴↑2)) = 𝐴)
 
Theoremsqsqrti 10864 Square of square root. (Contributed by NM, 11-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → ((√‘𝐴)↑2) = 𝐴)
 
Theoremsqrtge0i 10865 The square root of a nonnegative real is nonnegative. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → 0 ≤ (√‘𝐴))
 
Theoremabsidi 10866 A nonnegative number is its own absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (abs‘𝐴) = 𝐴)
 
Theoremabsnidi 10867 A negative number is the negative of its own absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       (𝐴 ≤ 0 → (abs‘𝐴) = -𝐴)
 
Theoremleabsi 10868 A real number is less than or equal to its absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       𝐴 ≤ (abs‘𝐴)
 
Theoremabsrei 10869 Absolute value of a real number. (Contributed by NM, 3-Aug-1999.)
𝐴 ∈ ℝ       (abs‘𝐴) = (√‘(𝐴↑2))
 
Theoremsqrtpclii 10870 The square root of a positive real is a real. (Contributed by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ    &   0 < 𝐴       (√‘𝐴) ∈ ℝ
 
Theoremsqrtgt0ii 10871 The square root of a positive real is positive. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ    &   0 < 𝐴       0 < (√‘𝐴)
 
Theoremsqrt11i 10872 The square root function is one-to-one. (Contributed by NM, 27-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → ((√‘𝐴) = (√‘𝐵) ↔ 𝐴 = 𝐵))
 
Theoremsqrtmuli 10873 Square root distributes over multiplication. (Contributed by NM, 30-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → (√‘(𝐴 · 𝐵)) = ((√‘𝐴) · (√‘𝐵)))
 
Theoremsqrtmulii 10874 Square root distributes over multiplication. (Contributed by NM, 30-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ    &   0 ≤ 𝐴    &   0 ≤ 𝐵       (√‘(𝐴 · 𝐵)) = ((√‘𝐴) · (√‘𝐵))
 
Theoremsqrtmsq2i 10875 Relationship between square root and squares. (Contributed by NM, 31-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → ((√‘𝐴) = 𝐵𝐴 = (𝐵 · 𝐵)))
 
Theoremsqrtlei 10876 Square root is monotonic. (Contributed by NM, 3-Aug-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → (𝐴𝐵 ↔ (√‘𝐴) ≤ (√‘𝐵)))
 
Theoremsqrtlti 10877 Square root is strictly monotonic. (Contributed by Roy F. Longton, 8-Aug-2005.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → (𝐴 < 𝐵 ↔ (√‘𝐴) < (√‘𝐵)))
 
Theoremabslti 10878 Absolute value and 'less than' relation. (Contributed by NM, 6-Apr-2005.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((abs‘𝐴) < 𝐵 ↔ (-𝐵 < 𝐴𝐴 < 𝐵))
 
Theoremabslei 10879 Absolute value and 'less than or equal to' relation. (Contributed by NM, 6-Apr-2005.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((abs‘𝐴) ≤ 𝐵 ↔ (-𝐵𝐴𝐴𝐵))
 
Theoremabsvalsqi 10880 Square of value of absolute value function. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       ((abs‘𝐴)↑2) = (𝐴 · (∗‘𝐴))
 
Theoremabsvalsq2i 10881 Square of value of absolute value function. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       ((abs‘𝐴)↑2) = (((ℜ‘𝐴)↑2) + ((ℑ‘𝐴)↑2))
 
Theoremabscli 10882 Real closure of absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       (abs‘𝐴) ∈ ℝ
 
Theoremabsge0i 10883 Absolute value is nonnegative. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       0 ≤ (abs‘𝐴)
 
Theoremabsval2i 10884 Value of absolute value function. Definition 10.36 of [Gleason] p. 133. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       (abs‘𝐴) = (√‘(((ℜ‘𝐴)↑2) + ((ℑ‘𝐴)↑2)))
 
Theoremabs00i 10885 The absolute value of a number is zero iff the number is zero. Proposition 10-3.7(c) of [Gleason] p. 133. (Contributed by NM, 28-Jul-1999.)
𝐴 ∈ ℂ       ((abs‘𝐴) = 0 ↔ 𝐴 = 0)
 
Theoremabsgt0api 10886 The absolute value of a nonzero number is positive. Remark in [Apostol] p. 363. (Contributed by NM, 1-Oct-1999.)
𝐴 ∈ ℂ       (𝐴 # 0 ↔ 0 < (abs‘𝐴))
 
Theoremabsnegi 10887 Absolute value of negative. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       (abs‘-𝐴) = (abs‘𝐴)
 
Theoremabscji 10888 The absolute value of a number and its conjugate are the same. Proposition 10-3.7(b) of [Gleason] p. 133. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       (abs‘(∗‘𝐴)) = (abs‘𝐴)
 
Theoremreleabsi 10889 The real part of a number is less than or equal to its absolute value. Proposition 10-3.7(d) of [Gleason] p. 133. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       (ℜ‘𝐴) ≤ (abs‘𝐴)
 
Theoremabssubi 10890 Swapping order of subtraction doesn't change the absolute value. Example of [Apostol] p. 363. (Contributed by NM, 1-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       (abs‘(𝐴𝐵)) = (abs‘(𝐵𝐴))
 
Theoremabsmuli 10891 Absolute value distributes over multiplication. Proposition 10-3.7(f) of [Gleason] p. 133. (Contributed by NM, 1-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       (abs‘(𝐴 · 𝐵)) = ((abs‘𝐴) · (abs‘𝐵))
 
Theoremsqabsaddi 10892 Square of absolute value of sum. Proposition 10-3.7(g) of [Gleason] p. 133. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       ((abs‘(𝐴 + 𝐵))↑2) = ((((abs‘𝐴)↑2) + ((abs‘𝐵)↑2)) + (2 · (ℜ‘(𝐴 · (∗‘𝐵)))))
 
Theoremsqabssubi 10893 Square of absolute value of difference. (Contributed by Steve Rodriguez, 20-Jan-2007.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       ((abs‘(𝐴𝐵))↑2) = ((((abs‘𝐴)↑2) + ((abs‘𝐵)↑2)) − (2 · (ℜ‘(𝐴 · (∗‘𝐵)))))
 
Theoremabsdivapzi 10894 Absolute value distributes over division. (Contributed by Jim Kingdon, 13-Aug-2021.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       (𝐵 # 0 → (abs‘(𝐴 / 𝐵)) = ((abs‘𝐴) / (abs‘𝐵)))
 
Theoremabstrii 10895 Triangle inequality for absolute value. Proposition 10-3.7(h) of [Gleason] p. 133. This is Metamath 100 proof #91. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       (abs‘(𝐴 + 𝐵)) ≤ ((abs‘𝐴) + (abs‘𝐵))
 
Theoremabs3difi 10896 Absolute value of differences around common element. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ    &   𝐶 ∈ ℂ       (abs‘(𝐴𝐵)) ≤ ((abs‘(𝐴𝐶)) + (abs‘(𝐶𝐵)))
 
Theoremabs3lemi 10897 Lemma involving absolute value of differences. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ    &   𝐶 ∈ ℂ    &   𝐷 ∈ ℝ       (((abs‘(𝐴𝐶)) < (𝐷 / 2) ∧ (abs‘(𝐶𝐵)) < (𝐷 / 2)) → (abs‘(𝐴𝐵)) < 𝐷)
 
Theoremrpsqrtcld 10898 The square root of a positive real is positive. (Contributed by Mario Carneiro, 29-May-2016.)
(𝜑𝐴 ∈ ℝ+)       (𝜑 → (√‘𝐴) ∈ ℝ+)
 
Theoremsqrtgt0d 10899 The square root of a positive real is positive. (Contributed by Mario Carneiro, 29-May-2016.)
(𝜑𝐴 ∈ ℝ+)       (𝜑 → 0 < (√‘𝐴))
 
Theoremabsnidd 10900 A negative number is the negative of its own absolute value. (Contributed by Mario Carneiro, 29-May-2016.)
(𝜑𝐴 ∈ ℝ)    &   (𝜑𝐴 ≤ 0)       (𝜑 → (abs‘𝐴) = -𝐴)
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