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Theorem List for Intuitionistic Logic Explorer - 10801-10900   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremresqrexlemnmsq 10801* Lemma for resqrex 10810. 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 10802* Lemma for resqrex 10810. 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 10803* Lemma for resqrex 10810. 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 10804* Lemma for resqrex 10810. 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 10805* Lemma for resqrex 10810. 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 10806* Lemma for resqrex 10810. 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 10807* Lemma for resqrex 10810. 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 10808* Lemma for resqrex 10810. 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 10809* Lemma for resqrex 10810. 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 10810* 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 10811* 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 10812* 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 10813 Closure of the square root function. (Contributed by Mario Carneiro, 9-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( sqr `  A )  e.  RR )
 
Theoremrersqrtthlem 10814 Lemma for resqrtth 10815. (Contributed by Jim Kingdon, 10-Aug-2021.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( ( sqr `  A ) ^ 2 )  =  A  /\  0  <_  ( sqr `  A )
 ) )
 
Theoremresqrtth 10815 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 10816 Square of square root. (Contributed by Mario Carneiro, 10-Jul-2013.)
 |-  ( ( A  e.  RR  /\  0  <_  A )  ->  ( ( sqr `  A )  x.  ( sqr `  A ) )  =  A )
 
Theoremsqrtge0 10817 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 10818 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 10819 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 10820 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 10821 Square root is strictly monotonic. Closed form of sqrtlti 10921. (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 10822 Analogue to sqrt11 10823 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 10823 The square root function is one-to-one. Also see sqrt11ap 10822 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 10824 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 10825 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 10826 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 10827 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 10828 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 10829 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 10830 The square root of 1 is 1. (Contributed by NM, 31-Jul-1999.)
 |-  ( sqr `  1
 )  =  1
 
Theoremsqrt4 10831 The square root of 4 is 2. (Contributed by NM, 3-Aug-1999.)
 |-  ( sqr `  4
 )  =  2
 
Theoremsqrt9 10832 The square root of 9 is 3. (Contributed by NM, 11-May-2004.)
 |-  ( sqr `  9
 )  =  3
 
Theoremsqrt2gt1lt2 10833 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 10834 Absolute value of negative. (Contributed by NM, 27-Feb-2005.)
 |-  ( A  e.  CC  ->  ( abs `  -u A )  =  ( abs `  A ) )
 
Theoremabscl 10835 Real closure of absolute value. (Contributed by NM, 3-Oct-1999.)
 |-  ( A  e.  CC  ->  ( abs `  A )  e.  RR )
 
Theoremabscj 10836 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 10837 Square of value of absolute value function. (Contributed by NM, 16-Jan-2006.)
 |-  ( A  e.  CC  ->  ( ( abs `  A ) ^ 2 )  =  ( A  x.  ( * `  A ) ) )
 
Theoremabsvalsq2 10838 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 10839 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 10840 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 10841 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 10842 The absolute value of 0. (Contributed by NM, 26-Mar-2005.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( abs `  0
 )  =  0
 
Theoremabsi 10843 The absolute value of the imaginary unit. (Contributed by NM, 26-Mar-2005.)
 |-  ( abs `  _i )  =  1
 
Theoremabsge0 10844 Absolute value is nonnegative. (Contributed by NM, 20-Nov-2004.) (Revised by Mario Carneiro, 29-May-2016.)
 |-  ( A  e.  CC  ->  0  <_  ( abs `  A ) )
 
Theoremabsrpclap 10845 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 10846 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 10847 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 10848 The absolute value of a number is zero iff the number is zero. Also see abs00ap 10846 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 10849 A complex number is zero iff its absolute value is zero. Deduction form of abs00 10848. (Contributed by David Moews, 28-Feb-2017.)
 |-  ( ph  ->  A  e.  CC )   =>    |-  ( ph  ->  (
 ( abs `  A )  =  0  <->  A  =  0
 ) )
 
Theoremabs00bd 10850 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 10851 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 10852 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 10853 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 10854 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 10855 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 10856 The absolute value of 1. Common special case. (Contributed by David A. Wheeler, 16-Jul-2016.)
 |-  ( abs `  1
 )  =  1
 
Theoremabsnid 10857 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 10858 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 10859 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 10860 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 10861 Absolute value of a real number. (Contributed by NM, 17-Mar-2005.)
 |-  ( A  e.  RR  ->  ( abs `  A )  =  ( sqr `  ( A ^ 2
 ) ) )
 
Theoremabsresq 10862 Square of the absolute value of a real number. (Contributed by NM, 16-Jan-2006.)
 |-  ( A  e.  RR  ->  ( ( abs `  A ) ^ 2 )  =  ( A ^ 2
 ) )
 
Theoremabsexp 10863 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 10864 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 10865 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 10866 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 10867 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 10868 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 10869 The absolute value of an integer is a nonnegative integer. (Contributed by NM, 27-Feb-2005.)
 |-  ( A  e.  ZZ  ->  ( abs `  A )  e.  NN0 )
 
Theoremzabscl 10870 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 10871 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 10872 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 10873 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 10874 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 10875 If the absolute value of a complex number is less than a real, its difference from the real is nonzero. See also abssubap0 10874 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 )
 
Theoremabsdiflt 10876 The absolute value of a difference and 'less than' relation. (Contributed by Paul Chapman, 18-Sep-2007.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  C  e.  RR )  ->  ( ( abs `  ( A  -  B ) )  <  C  <->  ( ( B  -  C )  <  A  /\  A  <  ( B  +  C )
 ) ) )
 
Theoremabsdifle 10877 The absolute value of a difference and 'less than or equal to' relation. (Contributed by Paul Chapman, 18-Sep-2007.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  C  e.  RR )  ->  ( ( abs `  ( A  -  B ) ) 
 <_  C  <->  ( ( B  -  C )  <_  A  /\  A  <_  ( B  +  C )
 ) ) )
 
Theoremelicc4abs 10878 Membership in a symmetric closed real interval. (Contributed by Stefan O'Rear, 16-Nov-2014.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  C  e.  RR )  ->  ( C  e.  (
 ( A  -  B ) [,] ( A  +  B ) )  <->  ( abs `  ( C  -  A ) ) 
 <_  B ) )
 
Theoremlenegsq 10879 Comparison to a nonnegative number based on comparison to squares. (Contributed by NM, 16-Jan-2006.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  0  <_  B )  ->  ( ( A  <_  B 
 /\  -u A  <_  B ) 
 <->  ( A ^ 2
 )  <_  ( B ^ 2 ) ) )
 
Theoremreleabs 10880 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  e.  CC  ->  ( Re `  A )  <_  ( abs `  A ) )
 
Theoremrecvalap 10881 Reciprocal expressed with a real denominator. (Contributed by Jim Kingdon, 13-Aug-2021.)
 |-  ( ( A  e.  CC  /\  A #  0 ) 
 ->  ( 1  /  A )  =  ( ( * `  A )  /  ( ( abs `  A ) ^ 2 ) ) )
 
Theoremabsidm 10882 The absolute value function is idempotent. (Contributed by NM, 20-Nov-2004.)
 |-  ( A  e.  CC  ->  ( abs `  ( abs `  A ) )  =  ( abs `  A ) )
 
Theoremabsgt0ap 10883 The absolute value of a number apart from zero is positive. (Contributed by Jim Kingdon, 13-Aug-2021.)
 |-  ( A  e.  CC  ->  ( A #  0  <->  0  <  ( abs `  A ) ) )
 
Theoremnnabscl 10884 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  e.  ZZ  /\  N  =/=  0
 )  ->  ( abs `  N )  e.  NN )
 
Theoremabssub 10885 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  e.  CC  /\  B  e.  CC )  ->  ( abs `  ( A  -  B ) )  =  ( abs `  ( B  -  A ) ) )
 
Theoremabssubge0 10886 Absolute value of a nonnegative difference. (Contributed by NM, 14-Feb-2008.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  A  <_  B )  ->  ( abs `  ( B  -  A ) )  =  ( B  -  A ) )
 
Theoremabssuble0 10887 Absolute value of a nonpositive difference. (Contributed by FL, 3-Jan-2008.)
 |-  ( ( A  e.  RR  /\  B  e.  RR  /\  A  <_  B )  ->  ( abs `  ( A  -  B ) )  =  ( B  -  A ) )
 
Theoremabstri 10888 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  e.  CC  /\  B  e.  CC )  ->  ( abs `  ( A  +  B )
 )  <_  ( ( abs `  A )  +  ( abs `  B )
 ) )
 
Theoremabs3dif 10889 Absolute value of differences around common element. (Contributed by FL, 9-Oct-2006.)
 |-  ( ( A  e.  CC  /\  B  e.  CC  /\  C  e.  CC )  ->  ( abs `  ( A  -  B ) ) 
 <_  ( ( abs `  ( A  -  C ) )  +  ( abs `  ( C  -  B ) ) ) )
 
Theoremabs2dif 10890 Difference of absolute values. (Contributed by Paul Chapman, 7-Sep-2007.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( ( abs `  A )  -  ( abs `  B ) ) 
 <_  ( abs `  ( A  -  B ) ) )
 
Theoremabs2dif2 10891 Difference of absolute values. (Contributed by Mario Carneiro, 14-Apr-2016.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( abs `  ( A  -  B ) ) 
 <_  ( ( abs `  A )  +  ( abs `  B ) ) )
 
Theoremabs2difabs 10892 Absolute value of difference of absolute values. (Contributed by Paul Chapman, 7-Sep-2007.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( abs `  (
 ( abs `  A )  -  ( abs `  B ) ) )  <_  ( abs `  ( A  -  B ) ) )
 
Theoremrecan 10893* Cancellation law involving the real part of a complex number. (Contributed by NM, 12-May-2005.)
 |-  ( ( A  e.  CC  /\  B  e.  CC )  ->  ( A. x  e.  CC  ( Re `  ( x  x.  A ) )  =  ( Re `  ( x  x.  B ) )  <->  A  =  B ) )
 
Theoremabsf 10894 Mapping domain and codomain of the absolute value function. (Contributed by NM, 30-Aug-2007.) (Revised by Mario Carneiro, 7-Nov-2013.)
 |- 
 abs : CC --> RR
 
Theoremabs3lem 10895 Lemma involving absolute value of differences. (Contributed by NM, 2-Oct-1999.)
 |-  ( ( ( A  e.  CC  /\  B  e.  CC )  /\  ( C  e.  CC  /\  D  e.  RR ) )  ->  ( ( ( abs `  ( A  -  C ) )  <  ( D 
 /  2 )  /\  ( abs `  ( C  -  B ) )  < 
 ( D  /  2
 ) )  ->  ( abs `  ( A  -  B ) )  <  D ) )
 
Theoremfzomaxdiflem 10896 Lemma for fzomaxdif 10897. (Contributed by Stefan O'Rear, 6-Sep-2015.)
 |-  ( ( ( A  e.  ( C..^ D )  /\  B  e.  ( C..^ D ) )  /\  A  <_  B )  ->  ( abs `  ( B  -  A ) )  e.  ( 0..^ ( D  -  C ) ) )
 
Theoremfzomaxdif 10897 A bound on the separation of two points in a half-open range. (Contributed by Stefan O'Rear, 6-Sep-2015.)
 |-  ( ( A  e.  ( C..^ D )  /\  B  e.  ( C..^ D ) )  ->  ( abs `  ( A  -  B ) )  e.  ( 0..^ ( D  -  C ) ) )
 
Theoremcau3lem 10898* Lemma for cau3 10899. (Contributed by Mario Carneiro, 15-Feb-2014.) (Revised by Mario Carneiro, 1-May-2014.)
 |-  Z  C_  ZZ   &    |-  ( ta  ->  ps )   &    |-  ( ( F `
  k )  =  ( F `  j
 )  ->  ( ps  <->  ch ) )   &    |-  ( ( F `
  k )  =  ( F `  m )  ->  ( ps  <->  th ) )   &    |-  (
 ( ph  /\  ch  /\  ps )  ->  ( G `  ( ( F `  j ) D ( F `  k ) ) )  =  ( G `  ( ( F `  k ) D ( F `  j ) ) ) )   &    |-  ( ( ph  /\ 
 th  /\  ch )  ->  ( G `  (
 ( F `  m ) D ( F `  j ) ) )  =  ( G `  ( ( F `  j ) D ( F `  m ) ) ) )   &    |-  (
 ( ph  /\  ( ps 
 /\  th )  /\  ( ch  /\  x  e.  RR ) )  ->  ( ( ( G `  (
 ( F `  k
 ) D ( F `
  j ) ) )  <  ( x 
 /  2 )  /\  ( G `  ( ( F `  j ) D ( F `  m ) ) )  <  ( x  / 
 2 ) )  ->  ( G `  ( ( F `  k ) D ( F `  m ) ) )  <  x ) )   =>    |-  ( ph  ->  ( A. x  e.  RR+  E. j  e.  Z  A. k  e.  ( ZZ>= `  j )
 ( ta  /\  ( G `  ( ( F `
  k ) D ( F `  j
 ) ) )  < 
 x )  <->  A. x  e.  RR+  E. j  e.  Z  A. k  e.  ( ZZ>= `  j ) ( ta 
 /\  A. m  e.  ( ZZ>=
 `  k ) ( G `  ( ( F `  k ) D ( F `  m ) ) )  <  x ) ) )
 
Theoremcau3 10899* 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 10772 and friends.) (Contributed by Mario Carneiro, 15-Feb-2014.)
 |-  Z  =  ( ZZ>= `  M )   =>    |-  ( A. x  e.  RR+  E. j  e.  Z  A. k  e.  ( ZZ>= `  j ) ( ( F `  k )  e.  CC  /\  ( abs `  ( ( F `
  k )  -  ( F `  j ) ) )  <  x ) 
 <-> 
 A. x  e.  RR+  E. j  e.  Z  A. k  e.  ( ZZ>= `  j ) ( ( F `  k )  e.  CC  /\  A. m  e.  ( ZZ>= `  k ) ( abs `  ( ( F `  k )  -  ( F `  m ) ) )  <  x ) )
 
Theoremcau4 10900* Change the base of a Cauchy criterion. (Contributed by Mario Carneiro, 18-Mar-2014.)
 |-  Z  =  ( ZZ>= `  M )   &    |-  W  =  (
 ZZ>= `  N )   =>    |-  ( N  e.  Z  ->  ( A. x  e.  RR+  E. j  e.  Z  A. k  e.  ( ZZ>= `  j )
 ( ( F `  k )  e.  CC  /\  ( abs `  (
 ( F `  k
 )  -  ( F `
  j ) ) )  <  x )  <->  A. x  e.  RR+  E. j  e.  W  A. k  e.  ( ZZ>= `  j )
 ( ( F `  k )  e.  CC  /\  ( abs `  (
 ( F `  k
 )  -  ( F `
  j ) ) )  <  x ) ) )
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