Theorem iffalse 2367

Description: Value of the conditional operator when its first argument is false.

Assertion

Ref	Expression
iffalse	|- (-. ph -> if(ph, A, B) = B)

Proof of Theorem iffalse

Step	Hyp	Ref	Expression
1		dedlemb 763	. . 3 |- (-. ph -> (x e. B <-> ((x e. A /\ ph) \/ (x e. B /\ -. ph))))
2	1	abbi2dv 1578	. 2 |- (-. ph -> B = {x | ((x e. A /\ ph) \/ (x e. B /\ -. ph))})
3		df-if 2362	. 2 |- if(ph, A, B) = {x | ((x e. A /\ ph) \/ (x e. B /\ -. ph))}
4	2, 3	syl6reqr 1526	1 |- (-. ph -> if(ph, A, B) = B)

Syntax hints:  -. wn 2   -> wi 3   \/ wo 222   /\ wa 223   = wceq 956   e. wcel 958  {cab 1463  ifcif 2361

This theorem is referenced by:  ifbi 2371  elimif 2374  ifboth 2375  ifid 2376  ifswap 2382  elimhyp 2390  elimhyp2v 2391  elimhyp3v 2392  elimhyp4v 2393  elimdhyp 2395  keephyp2v 2397  keephyp3v 2398  elimdeloprv 4001  oevn0 4154  suppr 4590  unxpdomlem 4843  xrmax1 5909  xrmax2 5910  xrmin1 5911  xrmin2 5912  max1ALT 5916  expnnvalt 6572  absmaxt 6897  bcval4t 6961  bcclt 6972  znnen 7502  ruclem13 7522  ruclem20 7529  ruclem21 7530  metxpfval 7831  metxp 7834  dscmet 7918  spwnex3 8655

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 962  ax-gen 963  ax-8 964  ax-10 966  ax-12 968  ax-17 971  ax-4 973  ax-5o 975  ax-6o 978  ax-9o 1123  ax-10o 1140  ax-16 1210  ax-11o 1218  ax-ext 1459

This theorem depends on definitions:  df-bi 147  df-or 224  df-an 225  df-ex 981  df-sb 1172  df-clab 1464  df-cleq 1469  df-clel 1472  df-if 2362

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