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Theorem List for Metamath Proof Explorer - 13901-14000   *Has distinct variable group(s)
TypeLabelDescription
Statement

Theoremzabscl 13901 The absolute value of an integer is an integer. (Contributed by Stefan O'Rear, 24-Sep-2014.)
(𝐴 ∈ ℤ → (abs‘𝐴) ∈ ℤ)

Theoremabslt 13902 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 13903 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)))

Theoremabssubne0 13904 If the absolute value of a complex number is less than a real, its difference from the real is nonzero. (Contributed by NM, 2-Nov-2007.) (Proof shortened by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℝ ∧ (abs‘𝐴) < 𝐵) → (𝐵𝐴) ≠ 0)

Theoremabsdiflt 13905 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 13906 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 13907 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 13908 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 13909 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))

Theoremrecval 13910 Reciprocal expressed with a real denominator. (Contributed by Mario Carneiro, 1-Apr-2015.)
((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (1 / 𝐴) = ((∗‘𝐴) / ((abs‘𝐴)↑2)))

Theoremabsidm 13911 The absolute value function is idempotent. (Contributed by NM, 20-Nov-2004.)
(𝐴 ∈ ℂ → (abs‘(abs‘𝐴)) = (abs‘𝐴))

Theoremabsgt0 13912 The absolute value of a nonzero number is positive. (Contributed by NM, 1-Oct-1999.) (Proof shortened by Mario Carneiro, 29-May-2016.)
(𝐴 ∈ ℂ → (𝐴 ≠ 0 ↔ 0 < (abs‘𝐴)))

Theoremnnabscl 13913 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 13914 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 13915 Absolute value of a nonnegative difference. (Contributed by NM, 14-Feb-2008.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐴𝐵) → (abs‘(𝐵𝐴)) = (𝐵𝐴))

Theoremabssuble0 13916 Absolute value of a nonpositive difference. (Contributed by FL, 3-Jan-2008.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐴𝐵) → (abs‘(𝐴𝐵)) = (𝐵𝐴))

Theoremabsmax 13917 The maximum of two numbers using absolute value. (Contributed by NM, 7-Aug-2008.)
((𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ) → if(𝐴𝐵, 𝐵, 𝐴) = (((𝐴 + 𝐵) + (abs‘(𝐴𝐵))) / 2))

Theoremabstri 13918 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 13919 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 13920 Difference of absolute values. (Contributed by Paul Chapman, 7-Sep-2007.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((abs‘𝐴) − (abs‘𝐵)) ≤ (abs‘(𝐴𝐵)))

Theoremabs2dif2 13921 Difference of absolute values. (Contributed by Mario Carneiro, 14-Apr-2016.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → (abs‘(𝐴𝐵)) ≤ ((abs‘𝐴) + (abs‘𝐵)))

Theoremabs2difabs 13922 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)))

Theoremabs1m 13923* For any complex number, there exists a unit-magnitude multiplier that produces its absolute value. Part of proof of Theorem 13-2.12 of [Gleason] p. 195. (Contributed by NM, 26-Mar-2005.)
(𝐴 ∈ ℂ → ∃𝑥 ∈ ℂ ((abs‘𝑥) = 1 ∧ (abs‘𝐴) = (𝑥 · 𝐴)))

Theoremrecan 13924* 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 13925 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 13926 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))

Theoremabslem2 13927 Lemma involving absolute values. (Contributed by NM, 11-Oct-1999.) (Revised by Mario Carneiro, 29-May-2016.)
((𝐴 ∈ ℂ ∧ 𝐴 ≠ 0) → (((∗‘(𝐴 / (abs‘𝐴))) · 𝐴) + ((𝐴 / (abs‘𝐴)) · (∗‘𝐴))) = (2 · (abs‘𝐴)))

Theoremrddif 13928 The difference between a real number and its nearest integer is less than or equal to one half. (Contributed by Jeff Madsen, 2-Sep-2009.) (Proof shortened by Mario Carneiro, 14-Sep-2015.)
(𝐴 ∈ ℝ → (abs‘((⌊‘(𝐴 + (1 / 2))) − 𝐴)) ≤ (1 / 2))

Theoremabsrdbnd 13929 Bound on the absolute value of a real number rounded to the nearest integer. (Contributed by Jeff Madsen, 2-Sep-2009.) (Proof shortened by Mario Carneiro, 14-Sep-2015.)
(𝐴 ∈ ℝ → (abs‘(⌊‘(𝐴 + (1 / 2)))) ≤ ((⌊‘(abs‘𝐴)) + 1))

Theoremfzomaxdiflem 13930 Lemma for fzomaxdif 13931. (Contributed by Stefan O'Rear, 6-Sep-2015.)
(((𝐴 ∈ (𝐶..^𝐷) ∧ 𝐵 ∈ (𝐶..^𝐷)) ∧ 𝐴𝐵) → (abs‘(𝐵𝐴)) ∈ (0..^(𝐷𝐶)))

Theoremfzomaxdif 13931 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)))

Theoremuzin2 13932 The upper integers are closed under intersection. (Contributed by Mario Carneiro, 24-Dec-2013.)
((𝐴 ∈ ran ℤ𝐵 ∈ ran ℤ) → (𝐴𝐵) ∈ ran ℤ)

Theoremrexanuz 13933* Combine two different upper integer properties into one. (Contributed by Mario Carneiro, 25-Dec-2013.)
(∃𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)(𝜑𝜓) ↔ (∃𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)𝜑 ∧ ∃𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)𝜓))

Theoremrexanre 13934* Combine two different upper real properties into one. (Contributed by Mario Carneiro, 8-May-2016.)
(𝐴 ⊆ ℝ → (∃𝑗 ∈ ℝ ∀𝑘𝐴 (𝑗𝑘 → (𝜑𝜓)) ↔ (∃𝑗 ∈ ℝ ∀𝑘𝐴 (𝑗𝑘𝜑) ∧ ∃𝑗 ∈ ℝ ∀𝑘𝐴 (𝑗𝑘𝜓))))

Theoremrexfiuz 13935* Combine finitely many different upper integer properties into one. (Contributed by Mario Carneiro, 6-Jun-2014.)
(𝐴 ∈ Fin → (∃𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)∀𝑛𝐴 𝜑 ↔ ∀𝑛𝐴𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)𝜑))

Theoremrexuz3 13936* Restrict the base of the upper integers set to another upper integers set. (Contributed by Mario Carneiro, 26-Dec-2013.)
𝑍 = (ℤ𝑀)       (𝑀 ∈ ℤ → (∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜑 ↔ ∃𝑗 ∈ ℤ ∀𝑘 ∈ (ℤ𝑗)𝜑))

Theoremrexanuz2 13937* Combine two different upper integer properties into one. (Contributed by Mario Carneiro, 26-Dec-2013.)
𝑍 = (ℤ𝑀)       (∃𝑗𝑍𝑘 ∈ (ℤ𝑗)(𝜑𝜓) ↔ (∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜑 ∧ ∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜓))

Theoremr19.29uz 13938* A version of 19.29 1789 for upper integer quantifiers. (Contributed by Mario Carneiro, 10-Feb-2014.)
𝑍 = (ℤ𝑀)       ((∀𝑘𝑍 𝜑 ∧ ∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜓) → ∃𝑗𝑍𝑘 ∈ (ℤ𝑗)(𝜑𝜓))

Theoremr19.2uz 13939* A version of r19.2z 4012 for upper integer quantifiers. (Contributed by Mario Carneiro, 15-Feb-2014.)
𝑍 = (ℤ𝑀)       (∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜑 → ∃𝑘𝑍 𝜑)

Theoremrexuzre 13940* Convert an upper real quantifier to an upper integer quantifier. (Contributed by Mario Carneiro, 7-May-2016.)
𝑍 = (ℤ𝑀)       (𝑀 ∈ ℤ → (∃𝑗𝑍𝑘 ∈ (ℤ𝑗)𝜑 ↔ ∃𝑗 ∈ ℝ ∀𝑘𝑍 (𝑗𝑘𝜑)))

Theoremrexico 13941* Restrict the base of an upper real quantifier to an upper real set. (Contributed by Mario Carneiro, 12-May-2016.)
((𝐴 ⊆ ℝ ∧ 𝐵 ∈ ℝ) → (∃𝑗 ∈ (𝐵[,)+∞)∀𝑘𝐴 (𝑗𝑘𝜑) ↔ ∃𝑗 ∈ ℝ ∀𝑘𝐴 (𝑗𝑘𝜑)))

Theoremcau3lem 13942* Lemma for cau3 13943. (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 13943* 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 13933 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 13944* 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 13945* 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)

Theoremcaubnd 13946* A Cauchy sequence of complex numbers is bounded. (Contributed by NM, 4-Apr-2005.) (Revised by Mario Carneiro, 14-Feb-2014.)
𝑍 = (ℤ𝑀)       ((∀𝑘𝑍 (𝐹𝑘) ∈ ℂ ∧ ∀𝑥 ∈ ℝ+𝑗𝑍𝑘 ∈ (ℤ𝑗)(abs‘((𝐹𝑘) − (𝐹𝑗))) < 𝑥) → ∃𝑦 ∈ ℝ ∀𝑘𝑍 (abs‘(𝐹𝑘)) < 𝑦)

Theoremsqreulem 13947 Lemma for sqreu 13948: write a general complex square root in terms of the square root function over nonnegative reals. (Contributed by Mario Carneiro, 9-Jul-2013.)
𝐵 = ((√‘(abs‘𝐴)) · (((abs‘𝐴) + 𝐴) / (abs‘((abs‘𝐴) + 𝐴))))       ((𝐴 ∈ ℂ ∧ ((abs‘𝐴) + 𝐴) ≠ 0) → ((𝐵↑2) = 𝐴 ∧ 0 ≤ (ℜ‘𝐵) ∧ (i · 𝐵) ∉ ℝ+))

Theoremsqreu 13948* Existence and uniqueness for the square root function in general. (Contributed by Mario Carneiro, 9-Jul-2013.)
(𝐴 ∈ ℂ → ∃!𝑥 ∈ ℂ ((𝑥↑2) = 𝐴 ∧ 0 ≤ (ℜ‘𝑥) ∧ (i · 𝑥) ∉ ℝ+))

Theoremsqrtcl 13949 Closure of the square root function over the complex numbers. (Contributed by Mario Carneiro, 10-Jul-2013.)
(𝐴 ∈ ℂ → (√‘𝐴) ∈ ℂ)

Theoremsqrtthlem 13950 Lemma for sqrtth 13952. (Contributed by Mario Carneiro, 10-Jul-2013.)
(𝐴 ∈ ℂ → (((√‘𝐴)↑2) = 𝐴 ∧ 0 ≤ (ℜ‘(√‘𝐴)) ∧ (i · (√‘𝐴)) ∉ ℝ+))

Theoremsqrtf 13951 Mapping domain and codomain of the square root function. (Contributed by Mario Carneiro, 13-Sep-2015.)
√:ℂ⟶ℂ

Theoremsqrtth 13952 Square root theorem over the complex numbers. Theorem I.35 of [Apostol] p. 29. (Contributed by Mario Carneiro, 10-Jul-2013.)
(𝐴 ∈ ℂ → ((√‘𝐴)↑2) = 𝐴)

Theoremsqrtrege0 13953 The square root function must make a choice between the two roots, which differ by a sign change. In the general complex case, the choice of "positive" and "negative" is not so clear. The convention we use is to take the root with positive real part, unless 𝐴 is a nonpositive real (in which case both roots have 0 real part); in this case we take the one in the positive imaginary direction. Another way to look at this is that we choose the root that is largest with respect to lexicographic order on the complex numbers (sorting by real part first, then by imaginary part as tie-breaker). (Contributed by Mario Carneiro, 10-Jul-2013.)
(𝐴 ∈ ℂ → 0 ≤ (ℜ‘(√‘𝐴)))

Theoremeqsqrtor 13954 Solve an equation containing a square. (Contributed by Mario Carneiro, 23-Apr-2015.)
((𝐴 ∈ ℂ ∧ 𝐵 ∈ ℂ) → ((𝐴↑2) = 𝐵 ↔ (𝐴 = (√‘𝐵) ∨ 𝐴 = -(√‘𝐵))))

Theoremeqsqrtd 13955 A deduction for showing that a number equals the square root of another. (Contributed by Mario Carneiro, 3-Apr-2015.)
(𝜑𝐴 ∈ ℂ)    &   (𝜑𝐵 ∈ ℂ)    &   (𝜑 → (𝐴↑2) = 𝐵)    &   (𝜑 → 0 ≤ (ℜ‘𝐴))    &   (𝜑 → ¬ (i · 𝐴) ∈ ℝ+)       (𝜑𝐴 = (√‘𝐵))

Theoremeqsqrt2d 13956 A deduction for showing that a number equals the square root of another. (Contributed by Mario Carneiro, 3-Apr-2015.)
(𝜑𝐴 ∈ ℂ)    &   (𝜑𝐵 ∈ ℂ)    &   (𝜑 → (𝐴↑2) = 𝐵)    &   (𝜑 → 0 < (ℜ‘𝐴))       (𝜑𝐴 = (√‘𝐵))

Theoremamgm2 13957 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 13958 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 13959 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 13960 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 13961 Square root of square. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (√‘(𝐴 · 𝐴)) = 𝐴)

Theoremsqrtsqi 13962 Square root of square. (Contributed by NM, 11-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (√‘(𝐴↑2)) = 𝐴)

Theoremsqsqrti 13963 Square of square root. (Contributed by NM, 11-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → ((√‘𝐴)↑2) = 𝐴)

Theoremsqrtge0i 13964 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 13965 A nonnegative number is its own absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       (0 ≤ 𝐴 → (abs‘𝐴) = 𝐴)

Theoremabsnidi 13966 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 13967 A real number is less than or equal to its absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℝ       𝐴 ≤ (abs‘𝐴)

Theoremabsori 13968 The absolute value of a real number is either that number or its negative. (Contributed by NM, 30-Sep-1999.)
𝐴 ∈ ℝ       ((abs‘𝐴) = 𝐴 ∨ (abs‘𝐴) = -𝐴)

Theoremabsrei 13969 Absolute value of a real number. (Contributed by NM, 3-Aug-1999.)
𝐴 ∈ ℝ       (abs‘𝐴) = (√‘(𝐴↑2))

Theoremsqrtpclii 13970 The square root of a positive real is a real. (Contributed by Mario Carneiro, 6-Sep-2013.)
𝐴 ∈ ℝ    &   0 < 𝐴       (√‘𝐴) ∈ ℝ

Theoremsqrtgt0ii 13971 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 13972 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 13973 Square root distributes over multiplication. (Contributed by NM, 30-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → (√‘(𝐴 · 𝐵)) = ((√‘𝐴) · (√‘𝐵)))

Theoremsqrtmulii 13974 Square root distributes over multiplication. (Contributed by NM, 30-Jul-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ    &   0 ≤ 𝐴    &   0 ≤ 𝐵       (√‘(𝐴 · 𝐵)) = ((√‘𝐴) · (√‘𝐵))

Theoremsqrtmsq2i 13975 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 13976 Square root is monotonic. (Contributed by NM, 3-Aug-1999.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((0 ≤ 𝐴 ∧ 0 ≤ 𝐵) → (𝐴𝐵 ↔ (√‘𝐴) ≤ (√‘𝐵)))

Theoremsqrtlti 13977 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 13978 Absolute value and 'less than' relation. (Contributed by NM, 6-Apr-2005.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((abs‘𝐴) < 𝐵 ↔ (-𝐵 < 𝐴𝐴 < 𝐵))

Theoremabslei 13979 Absolute value and 'less than or equal to' relation. (Contributed by NM, 6-Apr-2005.)
𝐴 ∈ ℝ    &   𝐵 ∈ ℝ       ((abs‘𝐴) ≤ 𝐵 ↔ (-𝐵𝐴𝐴𝐵))

Theoremabsvalsqi 13980 Square of value of absolute value function. (Contributed by NM, 2-Oct-1999.)
𝐴 ∈ ℂ       ((abs‘𝐴)↑2) = (𝐴 · (∗‘𝐴))

Theoremabsvalsq2i 13981 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 13982 Real closure of absolute value. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       (abs‘𝐴) ∈ ℝ

Theoremabsge0i 13983 Absolute value is nonnegative. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       0 ≤ (abs‘𝐴)

Theoremabsval2i 13984 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 13985 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)

Theoremabsgt0i 13986 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 13987 Absolute value of negative. (Contributed by NM, 2-Aug-1999.)
𝐴 ∈ ℂ       (abs‘-𝐴) = (abs‘𝐴)

Theoremabscji 13988 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 13989 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 13990 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 13991 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 13992 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 13993 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)))))

Theoremabsdivzi 13994 Absolute value distributes over division. (Contributed by NM, 26-Mar-2005.)
𝐴 ∈ ℂ    &   𝐵 ∈ ℂ       (𝐵 ≠ 0 → (abs‘(𝐴 / 𝐵)) = ((abs‘𝐴) / (abs‘𝐵)))

Theoremabstrii 13995 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 13996 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 13997 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 13998 The square root of a positive real is positive. (Contributed by Mario Carneiro, 29-May-2016.)
(𝜑𝐴 ∈ ℝ+)       (𝜑 → (√‘𝐴) ∈ ℝ+)

Theoremsqrtgt0d 13999 The square root of a positive real is positive. (Contributed by Mario Carneiro, 29-May-2016.)
(𝜑𝐴 ∈ ℝ+)       (𝜑 → 0 < (√‘𝐴))

Theoremabsnidd 14000 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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