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Theorem List for Intuitionistic Logic Explorer - 11001-11100   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremr19.29uz 11001* A version of 19.29 1620 for upper integer quantifiers. (Contributed by Mario Carneiro, 10-Feb-2014.)
 |-  Z  =  ( ZZ>= `  M )   =>    |-  ( ( A. k  e.  Z  ph  /\  E. j  e.  Z  A. k  e.  ( ZZ>= `  j ) ps )  ->  E. j  e.  Z  A. k  e.  ( ZZ>= `  j )
 ( ph  /\  ps )
 )
 
Theoremr19.2uz 11002* A version of r19.2m 3510 for upper integer quantifiers. (Contributed by Mario Carneiro, 15-Feb-2014.)
 |-  Z  =  ( ZZ>= `  M )   =>    |-  ( E. j  e.  Z  A. k  e.  ( ZZ>= `  j ) ph  ->  E. k  e.  Z  ph )
 
Theoremrecvguniqlem 11003 Lemma for recvguniq 11004. Some of the rearrangements of the expressions. (Contributed by Jim Kingdon, 8-Aug-2021.)
 |-  ( ph  ->  F : NN --> RR )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  B  e.  RR )   &    |-  ( ph  ->  K  e.  NN )   &    |-  ( ph  ->  A  <  (
 ( F `  K )  +  ( ( A  -  B )  / 
 2 ) ) )   &    |-  ( ph  ->  ( F `  K )  <  ( B  +  ( ( A  -  B )  / 
 2 ) ) )   =>    |-  ( ph  -> F.  )
 
Theoremrecvguniq 11004* Limits are unique. (Contributed by Jim Kingdon, 7-Aug-2021.)
 |-  ( ph  ->  F : NN --> RR )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. x  e.  RR+  E. j  e. 
 NN  A. k  e.  ( ZZ>=
 `  j ) ( ( F `  k
 )  <  ( L  +  x )  /\  L  <  ( ( F `  k )  +  x ) ) )   &    |-  ( ph  ->  M  e.  RR )   &    |-  ( ph  ->  A. x  e.  RR+  E. j  e. 
 NN  A. k  e.  ( ZZ>=
 `  j ) ( ( F `  k
 )  <  ( M  +  x )  /\  M  <  ( ( F `  k )  +  x ) ) )   =>    |-  ( ph  ->  L  =  M )
 
4.7.4  Square root; absolute value
 
Syntaxcsqrt 11005 Extend class notation to include square root of a complex number.
 class  sqr
 
Syntaxcabs 11006 Extend class notation to include a function for the absolute value (modulus) of a complex number.
 class  abs
 
Definitiondf-rsqrt 11007* Define a function whose value is the square root of a nonnegative real number.

Defining the square root for complex numbers has one difficult part: choosing between the two roots. The usual way to define a principal square root for all complex numbers relies on excluded middle or something similar. But in the case of a nonnegative real number, we don't have the complications presented for general complex numbers, and we can choose the nonnegative root.

(Contributed by Jim Kingdon, 23-Aug-2020.)

 |- 
 sqr  =  ( x  e.  RR  |->  ( iota_ y  e. 
 RR  ( ( y ^ 2 )  =  x  /\  0  <_  y ) ) )
 
Definitiondf-abs 11008 Define the function for the absolute value (modulus) of a complex number. (Contributed by NM, 27-Jul-1999.)
 |- 
 abs  =  ( x  e.  CC  |->  ( sqr `  ( x  x.  ( * `  x ) ) ) )
 
Theoremsqrtrval 11009* Value of square root function. (Contributed by Jim Kingdon, 23-Aug-2020.)
 |-  ( A  e.  RR  ->  ( sqr `  A )  =  ( iota_ x  e. 
 RR  ( ( x ^ 2 )  =  A  /\  0  <_  x ) ) )
 
Theoremabsval 11010 The absolute value (modulus) of a complex number. Proposition 10-3.7(a) of [Gleason] p. 133. (Contributed by NM, 27-Jul-1999.) (Revised by Mario Carneiro, 7-Nov-2013.)
 |-  ( A  e.  CC  ->  ( abs `  A )  =  ( sqr `  ( A  x.  ( * `  A ) ) ) )
 
Theoremrennim 11011 A real number does not lie on the negative imaginary axis. (Contributed by Mario Carneiro, 8-Jul-2013.)
 |-  ( A  e.  RR  ->  ( _i  x.  A )  e/  RR+ )
 
Theoremsqrt0rlem 11012 Lemma for sqrt0 11013. (Contributed by Jim Kingdon, 26-Aug-2020.)
 |-  ( ( A  e.  RR  /\  ( ( A ^ 2 )  =  0  /\  0  <_  A ) )  <->  A  =  0
 )
 
Theoremsqrt0 11013 Square root of zero. (Contributed by Mario Carneiro, 9-Jul-2013.)
 |-  ( sqr `  0
 )  =  0
 
Theoremresqrexlem1arp 11014 Lemma for resqrex 11035.  1  +  A is a positive real (expressed in a way that will help apply seqf 10461 and similar theorems). (Contributed by Jim Kingdon, 28-Jul-2021.) (Revised by Jim Kingdon, 16-Oct-2022.)
 |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0 
 <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  (
 ( NN  X.  {
 ( 1  +  A ) } ) `  N )  e.  RR+ )
 
Theoremresqrexlemp1rp 11015* Lemma for resqrex 11035. Applying the recursion rule yields a positive real (expressed in a way that will help apply seqf 10461 and similar theorems). (Contributed by Jim Kingdon, 28-Jul-2021.) (Revised by Jim Kingdon, 16-Oct-2022.)
 |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0 
 <_  A )   =>    |-  ( ( ph  /\  ( B  e.  RR+  /\  C  e.  RR+ ) )  ->  ( B ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) C )  e.  RR+ )
 
Theoremresqrexlemf 11016* Lemma for resqrex 11035. The sequence is a function. (Contributed by Mario Carneiro and Jim Kingdon, 27-Jul-2021.) (Revised by Jim Kingdon, 16-Oct-2022.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ph  ->  F : NN --> RR+ )
 
Theoremresqrexlemf1 11017* Lemma for resqrex 11035. Initial value. Although this sequence converges to the square root with any positive initial value, this choice makes various steps in the proof of convergence easier. (Contributed by Mario Carneiro and Jim Kingdon, 27-Jul-2021.) (Revised by Jim Kingdon, 16-Oct-2022.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ph  ->  ( F `  1 )  =  ( 1  +  A ) )
 
Theoremresqrexlemfp1 11018* Lemma for resqrex 11035. Recursion rule. This sequence is the ancient method for computing square roots, often known as the babylonian method, although known to many ancient cultures. (Contributed by Mario Carneiro and Jim Kingdon, 27-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  ( F `  ( N  +  1 ) )  =  ( ( ( F `
  N )  +  ( A  /  ( F `  N ) ) )  /  2 ) )
 
Theoremresqrexlemover 11019* Lemma for resqrex 11035. Each element of the sequence is an overestimate. (Contributed by Mario Carneiro and Jim Kingdon, 27-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  A  <  ( ( F `  N ) ^ 2
 ) )
 
Theoremresqrexlemdec 11020* Lemma for resqrex 11035. The sequence is decreasing. (Contributed by Mario Carneiro and Jim Kingdon, 29-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  ( F `  ( N  +  1 ) )  < 
 ( F `  N ) )
 
Theoremresqrexlemdecn 11021* Lemma for resqrex 11035. The sequence is decreasing. (Contributed by Jim Kingdon, 31-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  N  e.  NN )   &    |-  ( ph  ->  M  e.  NN )   &    |-  ( ph  ->  N  <  M )   =>    |-  ( ph  ->  ( F `  M )  < 
 ( F `  N ) )
 
Theoremresqrexlemlo 11022* Lemma for resqrex 11035. A (variable) lower bound for each term of the sequence. (Contributed by Mario Carneiro and Jim Kingdon, 29-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  (
 1  /  ( 2 ^ N ) )  < 
 ( F `  N ) )
 
Theoremresqrexlemcalc1 11023* Lemma for resqrex 11035. Some of the calculations involved in showing that the sequence converges. (Contributed by Mario Carneiro and Jim Kingdon, 29-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  (
 ( ( F `  ( N  +  1
 ) ) ^ 2
 )  -  A )  =  ( ( ( ( ( F `  N ) ^ 2
 )  -  A ) ^ 2 )  /  ( 4  x.  (
 ( F `  N ) ^ 2 ) ) ) )
 
Theoremresqrexlemcalc2 11024* Lemma for resqrex 11035. Some of the calculations involved in showing that the sequence converges. (Contributed by Mario Carneiro and Jim Kingdon, 29-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  (
 ( ( F `  ( N  +  1
 ) ) ^ 2
 )  -  A ) 
 <_  ( ( ( ( F `  N ) ^ 2 )  -  A )  /  4
 ) )
 
Theoremresqrexlemcalc3 11025* Lemma for resqrex 11035. Some of the calculations involved in showing that the sequence converges. (Contributed by Mario Carneiro and Jim Kingdon, 29-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ( ph  /\  N  e.  NN )  ->  (
 ( ( F `  N ) ^ 2
 )  -  A ) 
 <_  ( ( ( F `
  1 ) ^
 2 )  /  (
 4 ^ ( N  -  1 ) ) ) )
 
Theoremresqrexlemnmsq 11026* Lemma for resqrex 11035. The difference between the squares of two terms of the sequence. (Contributed by Mario Carneiro and Jim Kingdon, 30-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  N  e.  NN )   &    |-  ( ph  ->  M  e.  NN )   &    |-  ( ph  ->  N  <_  M )   =>    |-  ( ph  ->  (
 ( ( F `  N ) ^ 2
 )  -  ( ( F `  M ) ^ 2 ) )  <  ( ( ( F `  1 ) ^ 2 )  /  ( 4 ^ ( N  -  1 ) ) ) )
 
Theoremresqrexlemnm 11027* Lemma for resqrex 11035. The difference between two terms of the sequence. (Contributed by Mario Carneiro and Jim Kingdon, 31-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  N  e.  NN )   &    |-  ( ph  ->  M  e.  NN )   &    |-  ( ph  ->  N  <_  M )   =>    |-  ( ph  ->  (
 ( F `  N )  -  ( F `  M ) )  < 
 ( ( ( ( F `  1 ) ^ 2 )  x.  2 )  /  (
 2 ^ ( N  -  1 ) ) ) )
 
Theoremresqrexlemcvg 11028* Lemma for resqrex 11035. The sequence has a limit. (Contributed by Jim Kingdon, 6-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ph  ->  E. r  e.  RR  A. x  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j ) ( ( F `  i )  <  ( r  +  x )  /\  r  < 
 ( ( F `  i )  +  x ) ) )
 
Theoremresqrexlemgt0 11029* Lemma for resqrex 11035. A limit is nonnegative. (Contributed by Jim Kingdon, 7-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j )
 ( ( F `  i )  <  ( L  +  e )  /\  L  <  ( ( F `
  i )  +  e ) ) )   =>    |-  ( ph  ->  0  <_  L )
 
Theoremresqrexlemoverl 11030* Lemma for resqrex 11035. Every term in the sequence is an overestimate compared with the limit 
L. Although this theorem is stated in terms of a particular sequence the proof could be adapted for any decreasing convergent sequence. (Contributed by Jim Kingdon, 9-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j )
 ( ( F `  i )  <  ( L  +  e )  /\  L  <  ( ( F `
  i )  +  e ) ) )   &    |-  ( ph  ->  K  e.  NN )   =>    |-  ( ph  ->  L  <_  ( F `  K ) )
 
Theoremresqrexlemglsq 11031* Lemma for resqrex 11035. The sequence formed by squaring each term of  F converges to  ( L ^
2 ). (Contributed by Mario Carneiro and Jim Kingdon, 8-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j )
 ( ( F `  i )  <  ( L  +  e )  /\  L  <  ( ( F `
  i )  +  e ) ) )   &    |-  G  =  ( x  e.  NN  |->  ( ( F `
  x ) ^
 2 ) )   =>    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. k  e.  ( ZZ>= `  j )
 ( ( G `  k )  <  ( ( L ^ 2 )  +  e )  /\  ( L ^ 2 )  <  ( ( G `
  k )  +  e ) ) )
 
Theoremresqrexlemga 11032* Lemma for resqrex 11035. The sequence formed by squaring each term of  F converges to  A. (Contributed by Mario Carneiro and Jim Kingdon, 8-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j )
 ( ( F `  i )  <  ( L  +  e )  /\  L  <  ( ( F `
  i )  +  e ) ) )   &    |-  G  =  ( x  e.  NN  |->  ( ( F `
  x ) ^
 2 ) )   =>    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. k  e.  ( ZZ>= `  j )
 ( ( G `  k )  <  ( A  +  e )  /\  A  <  ( ( G `
  k )  +  e ) ) )
 
Theoremresqrexlemsqa 11033* Lemma for resqrex 11035. The square of a limit is  A. (Contributed by Jim Kingdon, 7-Aug-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   &    |-  ( ph  ->  L  e.  RR )   &    |-  ( ph  ->  A. e  e.  RR+  E. j  e.  NN  A. i  e.  ( ZZ>= `  j )
 ( ( F `  i )  <  ( L  +  e )  /\  L  <  ( ( F `
  i )  +  e ) ) )   =>    |-  ( ph  ->  ( L ^ 2 )  =  A )
 
Theoremresqrexlemex 11034* Lemma for resqrex 11035. Existence of square root given a sequence which converges to the square root. (Contributed by Mario Carneiro and Jim Kingdon, 27-Jul-2021.)
 |-  F  =  seq 1
 ( ( y  e.  RR+ ,  z  e.  RR+  |->  ( ( y  +  ( A  /  y
 ) )  /  2
 ) ) ,  ( NN  X.  { ( 1  +  A ) }
 ) )   &    |-  ( ph  ->  A  e.  RR )   &    |-  ( ph  ->  0  <_  A )   =>    |-  ( ph  ->  E. x  e.  RR  ( 0  <_  x  /\  ( x ^
 2 )  =  A ) )
 
Theoremresqrex 11035* Existence of a square root for positive reals. (Contributed by Mario Carneiro, 9-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  E. x  e.  RR  ( 0  <_  x  /\  ( x ^ 2
 )  =  A ) )
 
Theoremrsqrmo 11036* Uniqueness for the square root function. (Contributed by Jim Kingdon, 10-Aug-2021.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  E* x  e.  RR  ( ( x ^
 2 )  =  A  /\  0  <_  x ) )
 
Theoremrersqreu 11037* Existence and uniqueness for the real square root function. (Contributed by Jim Kingdon, 10-Aug-2021.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  E! x  e. 
 RR  ( ( x ^ 2 )  =  A  /\  0  <_  x ) )
 
Theoremresqrtcl 11038 Closure of the square root function. (Contributed by Mario Carneiro, 9-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( sqr `  A )  e.  RR )
 
Theoremrersqrtthlem 11039 Lemma for resqrtth 11040. (Contributed by Jim Kingdon, 10-Aug-2021.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( ( sqr `  A ) ^ 2 )  =  A  /\  0  <_  ( sqr `  A )
 ) )
 
Theoremresqrtth 11040 Square root theorem over the reals. Theorem I.35 of [Apostol] p. 29. (Contributed by Mario Carneiro, 9-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( sqr `  A ) ^ 2
 )  =  A )
 
Theoremremsqsqrt 11041 Square of square root. (Contributed by Mario Carneiro, 10-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( sqr `  A )  x.  ( sqr `  A ) )  =  A )
 
Theoremsqrtge0 11042 The square root function is nonnegative for nonnegative input. (Contributed by NM, 26-May-1999.) (Revised by Mario Carneiro, 9-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  0  <_  ( sqr `  A ) )
 
Theoremsqrtgt0 11043 The square root function is positive for positive input. (Contributed by Mario Carneiro, 10-Jul-2013.) (Revised by Mario Carneiro, 6-Sep-2013.)
 |-  ( ( A  e.  RR  /\  0  <  A )  ->  0  <  ( sqr `  A ) )
 
Theoremsqrtmul 11044 Square root distributes over multiplication. (Contributed by NM, 30-Jul-1999.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( sqr `  ( A  x.  B ) )  =  ( ( sqr `  A )  x.  ( sqr `  B ) ) )
 
Theoremsqrtle 11045 Square root is monotonic. (Contributed by NM, 17-Mar-2005.) (Proof shortened by Mario Carneiro, 29-May-2016.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( A  <_  B  <->  ( sqr `  A )  <_  ( sqr `  B ) ) )
 
Theoremsqrtlt 11046 Square root is strictly monotonic. Closed form of sqrtlti 11146. (Contributed by Scott Fenton, 17-Apr-2014.) (Proof shortened by Mario Carneiro, 29-May-2016.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( A  <  B  <->  ( sqr `  A )  <  ( sqr `  B ) ) )
 
Theoremsqrt11ap 11047 Analogue to sqrt11 11048 but for apartness. (Contributed by Jim Kingdon, 11-Aug-2021.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( ( sqr `  A ) #  ( sqr `  B ) 
 <->  A #  B ) )
 
Theoremsqrt11 11048 The square root function is one-to-one. Also see sqrt11ap 11047 which would follow easily from this given excluded middle, but which is proved another way without it. (Contributed by Scott Fenton, 11-Jun-2013.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( ( sqr `  A )  =  ( sqr `  B )  <->  A  =  B ) )
 
Theoremsqrt00 11049 A square root is zero iff its argument is 0. (Contributed by NM, 27-Jul-1999.) (Proof shortened by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( sqr `  A )  =  0  <->  A  =  0 )
 )
 
Theoremrpsqrtcl 11050 The square root of a positive real is a positive real. (Contributed by NM, 22-Feb-2008.)
 |-  ( A  e.  RR+  ->  ( sqr `  A )  e.  RR+ )
 
Theoremsqrtdiv 11051 Square root distributes over division. (Contributed by Mario Carneiro, 5-May-2016.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  B  e.  RR+ )  ->  ( sqr `  ( A  /  B ) )  =  ( ( sqr `  A )  /  ( sqr `  B ) ) )
 
Theoremsqrtsq2 11052 Relationship between square root and squares. (Contributed by NM, 31-Jul-1999.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( ( A  e.  RR  /\  0  <_  A )  /\  ( B  e.  RR  /\  0  <_  B ) )  ->  ( ( sqr `  A )  =  B  <->  A  =  ( B ^ 2 ) ) )
 
Theoremsqrtsq 11053 Square root of square. (Contributed by NM, 14-Jan-2006.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( sqr `  ( A ^ 2 ) )  =  A )
 
Theoremsqrtmsq 11054 Square root of square. (Contributed by NM, 2-Aug-1999.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( sqr `  ( A  x.  A ) )  =  A )
 
Theoremsqrt1 11055 The square root of 1 is 1. (Contributed by NM, 31-Jul-1999.)
 |-  ( sqr `  1
 )  =  1
 
Theoremsqrt4 11056 The square root of 4 is 2. (Contributed by NM, 3-Aug-1999.)
 |-  ( sqr `  4
 )  =  2
 
Theoremsqrt9 11057 The square root of 9 is 3. (Contributed by NM, 11-May-2004.)
 |-  ( sqr `  9
 )  =  3
 
Theoremsqrt2gt1lt2 11058 The square root of 2 is bounded by 1 and 2. (Contributed by Roy F. Longton, 8-Aug-2005.) (Revised by Mario Carneiro, 6-Sep-2013.)
 |-  ( 1  <  ( sqr `  2 )  /\  ( sqr `  2 )  <  2 )
 
Theoremabsneg 11059 Absolute value of negative. (Contributed by NM, 27-Feb-2005.)
 |-  ( A  e.  CC  ->  ( abs `  -u A )  =  ( abs `  A ) )
 
Theoremabscl 11060 Real closure of absolute value. (Contributed by NM, 3-Oct-1999.)
 |-  ( A  e.  CC  ->  ( abs `  A )  e.  RR )
 
Theoremabscj 11061 The absolute value of a number and its conjugate are the same. Proposition 10-3.7(b) of [Gleason] p. 133. (Contributed by NM, 28-Apr-2005.)
 |-  ( A  e.  CC  ->  ( abs `  ( * `  A ) )  =  ( abs `  A ) )
 
Theoremabsvalsq 11062 Square of value of absolute value function. (Contributed by NM, 16-Jan-2006.)
 |-  ( A  e.  CC  ->  ( ( abs `  A ) ^ 2 )  =  ( A  x.  ( * `  A ) ) )
 
Theoremabsvalsq2 11063 Square of value of absolute value function. (Contributed by NM, 1-Feb-2007.)
 |-  ( A  e.  CC  ->  ( ( abs `  A ) ^ 2 )  =  ( ( ( Re
 `  A ) ^
 2 )  +  (
 ( Im `  A ) ^ 2 ) ) )
 
Theoremsqabsadd 11064 Square of absolute value of sum. Proposition 10-3.7(g) of [Gleason] p. 133. (Contributed by NM, 21-Jan-2007.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( ( abs `  ( A  +  B ) ) ^ 2
 )  =  ( ( ( ( abs `  A ) ^ 2 )  +  ( ( abs `  B ) ^ 2 ) )  +  ( 2  x.  ( Re `  ( A  x.  ( * `  B ) ) ) ) ) )
 
Theoremsqabssub 11065 Square of absolute value of difference. (Contributed by NM, 21-Jan-2007.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( ( abs `  ( A  -  B ) ) ^ 2
 )  =  ( ( ( ( abs `  A ) ^ 2 )  +  ( ( abs `  B ) ^ 2 ) )  -  ( 2  x.  ( Re `  ( A  x.  ( * `  B ) ) ) ) ) )
 
Theoremabsval2 11066 Value of absolute value function. Definition 10.36 of [Gleason] p. 133. (Contributed by NM, 17-Mar-2005.)
 |-  ( A  e.  CC  ->  ( abs `  A )  =  ( sqr `  ( ( ( Re
 `  A ) ^
 2 )  +  (
 ( Im `  A ) ^ 2 ) ) ) )
 
Theoremabs0 11067 The absolute value of 0. (Contributed by NM, 26-Mar-2005.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( abs `  0
 )  =  0
 
Theoremabsi 11068 The absolute value of the imaginary unit. (Contributed by NM, 26-Mar-2005.)
 |-  ( abs `  _i )  =  1
 
Theoremabsge0 11069 Absolute value is nonnegative. (Contributed by NM, 20-Nov-2004.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( A  e.  CC  ->  0  <_  ( abs `  A ) )
 
Theoremabsrpclap 11070 The absolute value of a number apart from zero is a positive real. (Contributed by Jim Kingdon, 11-Aug-2021.)
 |-  ( ( A  e.  CC  /\  A #  0 ) 
 ->  ( abs `  A )  e.  RR+ )
 
Theoremabs00ap 11071 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  e.  CC  ->  ( ( abs `  A ) #  0  <->  A #  0 )
 )
 
Theoremabsext 11072 Strong extensionality for absolute value. (Contributed by Jim Kingdon, 12-Aug-2021.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( ( abs `  A ) #  ( abs `  B )  ->  A #  B ) )
 
Theoremabs00 11073 The absolute value of a number is zero iff the number is zero. Also see abs00ap 11071 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  e.  CC  ->  ( ( abs `  A )  =  0  <->  A  =  0
 ) )
 
Theoremabs00ad 11074 A complex number is zero iff its absolute value is zero. Deduction form of abs00 11073. (Contributed by David Moews, 28-Feb-2017.)
 |-  ( ph  ->  A  e.  CC )   =>    |-  ( ph  ->  (
 ( abs `  A )  =  0  <->  A  =  0
 ) )
 
Theoremabs00bd 11075 If a complex number is zero, its absolute value is zero. (Contributed by David Moews, 28-Feb-2017.)
 |-  ( ph  ->  A  =  0 )   =>    |-  ( ph  ->  ( abs `  A )  =  0 )
 
Theoremabsreimsq 11076 Square of the absolute value of a number that has been decomposed into real and imaginary parts. (Contributed by NM, 1-Feb-2007.)
 |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( abs `  ( A  +  ( _i  x.  B ) ) ) ^ 2 )  =  ( ( A ^ 2 )  +  ( B ^ 2 ) ) )
 
Theoremabsreim 11077 Absolute value of a number that has been decomposed into real and imaginary parts. (Contributed by NM, 14-Jan-2006.)
 |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( abs `  ( A  +  ( _i  x.  B ) ) )  =  ( sqr `  (
 ( A ^ 2
 )  +  ( B ^ 2 ) ) ) )
 
Theoremabsmul 11078 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  e.  CC  /\  B  e.  CC )  ->  ( abs `  ( A  x.  B ) )  =  ( ( abs `  A )  x.  ( abs `  B ) ) )
 
Theoremabsdivap 11079 Absolute value distributes over division. (Contributed by Jim Kingdon, 11-Aug-2021.)
 |-  ( ( A  e.  CC  /\  B  e.  CC  /\  B #  0 )  ->  ( abs `  ( A  /  B ) )  =  ( ( abs `  A )  /  ( abs `  B ) ) )
 
Theoremabsid 11080 A nonnegative number is its own absolute value. (Contributed by NM, 11-Oct-1999.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( abs `  A )  =  A )
 
Theoremabs1 11081 The absolute value of 1. Common special case. (Contributed by David A. Wheeler, 16-Jul-2016.)
 |-  ( abs `  1
 )  =  1
 
Theoremabsnid 11082 A negative number is the negative of its own absolute value. (Contributed by NM, 27-Feb-2005.)
 |-  ( ( A  e.  RR  /\  A  <_  0
 )  ->  ( abs `  A )  =  -u A )
 
Theoremleabs 11083 A real number is less than or equal to its absolute value. (Contributed by NM, 27-Feb-2005.)
 |-  ( A  e.  RR  ->  A  <_  ( abs `  A ) )
 
Theoremqabsor 11084 The absolute value of a rational number is either that number or its negative. (Contributed by Jim Kingdon, 8-Nov-2021.)
 |-  ( A  e.  QQ  ->  ( ( abs `  A )  =  A  \/  ( abs `  A )  =  -u A ) )
 
Theoremqabsord 11085 The absolute value of a rational number is either that number or its negative. (Contributed by Jim Kingdon, 8-Nov-2021.)
 |-  ( ph  ->  A  e.  QQ )   =>    |-  ( ph  ->  (
 ( abs `  A )  =  A  \/  ( abs `  A )  =  -u A ) )
 
Theoremabsre 11086 Absolute value of a real number. (Contributed by NM, 17-Mar-2005.)
 |-  ( A  e.  RR  ->  ( abs `  A )  =  ( sqr `  ( A ^ 2
 ) ) )
 
Theoremabsresq 11087 Square of the absolute value of a real number. (Contributed by NM, 16-Jan-2006.)
 |-  ( A  e.  RR  ->  ( ( abs `  A ) ^ 2 )  =  ( A ^ 2
 ) )
 
Theoremabsexp 11088 Absolute value of positive integer exponentiation. (Contributed by NM, 5-Jan-2006.)
 |-  ( ( A  e.  CC  /\  N  e.  NN0 )  ->  ( abs `  ( A ^ N ) )  =  ( ( abs `  A ) ^ N ) )
 
Theoremabsexpzap 11089 Absolute value of integer exponentiation. (Contributed by Jim Kingdon, 11-Aug-2021.)
 |-  ( ( A  e.  CC  /\  A #  0  /\  N  e.  ZZ )  ->  ( abs `  ( A ^ N ) )  =  ( ( abs `  A ) ^ N ) )
 
Theoremabssq 11090 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  e.  CC  ->  ( ( abs `  A ) ^ 2 )  =  ( abs `  ( A ^ 2 ) ) )
 
Theoremsqabs 11091 The squares of two reals are equal iff their absolute values are equal. (Contributed by NM, 6-Mar-2009.)
 |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( A ^ 2 )  =  ( B ^ 2
 ) 
 <->  ( abs `  A )  =  ( abs `  B ) ) )
 
Theoremabsrele 11092 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  e.  CC  ->  ( abs `  ( Re `  A ) ) 
 <_  ( abs `  A ) )
 
Theoremabsimle 11093 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  e.  CC  ->  ( abs `  ( Im `  A ) ) 
 <_  ( abs `  A ) )
 
Theoremnn0abscl 11094 The absolute value of an integer is a nonnegative integer. (Contributed by NM, 27-Feb-2005.)
 |-  ( A  e.  ZZ  ->  ( abs `  A )  e.  NN0 )
 
Theoremzabscl 11095 The absolute value of an integer is an integer. (Contributed by Stefan O'Rear, 24-Sep-2014.)
 |-  ( A  e.  ZZ  ->  ( abs `  A )  e.  ZZ )
 
Theoremltabs 11096 A number which is less than its absolute value is negative. (Contributed by Jim Kingdon, 12-Aug-2021.)
 |-  ( ( A  e.  RR  /\  A  <  ( abs `  A ) ) 
 ->  A  <  0 )
 
Theoremabslt 11097 Absolute value and 'less than' relation. (Contributed by NM, 6-Apr-2005.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( abs `  A )  <  B  <->  (
 -u B  <  A  /\  A  <  B ) ) )
 
Theoremabsle 11098 Absolute value and 'less than or equal to' relation. (Contributed by NM, 6-Apr-2005.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( ( A  e.  RR  /\  B  e.  RR )  ->  ( ( abs `  A )  <_  B  <->  (
 -u B  <_  A  /\  A  <_  B )
 ) )
 
Theoremabssubap0 11099 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  e.  CC  /\  B  e.  RR  /\  ( abs `  A )  <  B )  ->  ( B  -  A ) #  0 )
 
Theoremabssubne0 11100 If the absolute value of a complex number is less than a real, its difference from the real is nonzero. See also abssubap0 11099 which is the same with not equal changed to apart. (Contributed by NM, 2-Nov-2007.)
 |-  ( ( A  e.  CC  /\  B  e.  RR  /\  ( abs `  A )  <  B )  ->  ( B  -  A )  =/=  0 )
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