Theorem sqrtrege0 13198

Description: 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 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.)

Assertion

Ref	Expression
sqrtrege0

Proof of Theorem sqrtrege0

Step	Hyp	Ref	Expression
1		sqrtthlem 13195	. 2
2	1	simp2d 1009	1

Syntax hints:  ->wi 4  =wceq 1395  e.wcel 1818  e/wnel 2653   class class class wbr 4452  `cfv 5593  (class class class)co 6296  cc 9511  0cc0 9513  ci 9515  cmul 9518  cle 9650  2c2 10610  crp 11249  cexp 12166  cre 12930  csqrt 13066

This theorem is referenced by:  sqrtrege0d  13269  cxpsqrtlem  23083

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1618  ax-4 1631  ax-5 1704  ax-6 1747  ax-7 1790  ax-8 1820  ax-9 1822  ax-10 1837  ax-11 1842  ax-12 1854  ax-13 1999  ax-ext 2435  ax-sep 4573  ax-nul 4581  ax-pow 4630  ax-pr 4691  ax-un 6592  ax-cnex 9569  ax-resscn 9570  ax-1cn 9571  ax-icn 9572  ax-addcl 9573  ax-addrcl 9574  ax-mulcl 9575  ax-mulrcl 9576  ax-mulcom 9577  ax-addass 9578  ax-mulass 9579  ax-distr 9580  ax-i2m1 9581  ax-1ne0 9582  ax-1rid 9583  ax-rnegex 9584  ax-rrecex 9585  ax-cnre 9586  ax-pre-lttri 9587  ax-pre-lttrn 9588  ax-pre-ltadd 9589  ax-pre-mulgt0 9590  ax-pre-sup 9591

This theorem depends on definitions:  df-bi 185  df-or 370  df-an 371  df-3or 974  df-3an 975  df-tru 1398  df-ex 1613  df-nf 1617  df-sb 1740  df-eu 2286  df-mo 2287  df-clab 2443  df-cleq 2449  df-clel 2452  df-nfc 2607  df-ne 2654  df-nel 2655  df-ral 2812  df-rex 2813  df-reu 2814  df-rmo 2815  df-rab 2816  df-v 3111  df-sbc 3328  df-csb 3435  df-dif 3478  df-un 3480  df-in 3482  df-ss 3489  df-pss 3491  df-nul 3785  df-if 3942  df-pw 4014  df-sn 4030  df-pr 4032  df-tp 4034  df-op 4036  df-uni 4250  df-iun 4332  df-br 4453  df-opab 4511  df-mpt 4512  df-tr 4546  df-eprel 4796  df-id 4800  df-po 4805  df-so 4806  df-fr 4843  df-we 4845  df-ord 4886  df-on 4887  df-lim 4888  df-suc 4889  df-xp 5010  df-rel 5011  df-cnv 5012  df-co 5013  df-dm 5014  df-rn 5015  df-res 5016  df-ima 5017  df-iota 5556  df-fun 5595  df-fn 5596  df-f 5597  df-f1 5598  df-fo 5599  df-f1o 5600  df-fv 5601  df-riota 6257  df-ov 6299  df-oprab 6300  df-mpt2 6301  df-om 6701  df-2nd 6801  df-recs 7061  df-rdg 7095  df-er 7330  df-en 7537  df-dom 7538  df-sdom 7539  df-sup 7921  df-pnf 9651  df-mnf 9652  df-xr 9653  df-ltxr 9654  df-le 9655  df-sub 9830  df-neg 9831  df-div 10232  df-nn 10562  df-2 10619  df-3 10620  df-n0 10821  df-z 10890  df-uz 11111  df-rp 11250  df-seq 12108  df-exp 12167  df-cj 12932  df-re 12933  df-im 12934  df-sqrt 13068  df-abs 13069