Theorem pw1if 7356

Description: Expressing a truth value in terms of an if expression. (Contributed by Jim Kingdon, 10-Jan-2026.)

Assertion

Ref	Expression
pw1if	|- ( A e. ~P 1o -> if ( A = 1o , 1o , (/) ) = A )

Proof of Theorem pw1if

Dummy variables x y are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		simpr 110	. . . . . 6 |- ( ( A e. ~P 1o /\ x e. if ( A = 1o , 1o , (/) ) ) -> x e. if ( A = 1o , 1o , (/) ) )
2		elif 3587	. . . . . . 7 |- ( x e. if ( A = 1o , 1o , (/) ) <-> ( ( A = 1o /\ x e. 1o ) \/ ( -. A = 1o /\ x e. (/) ) ) )
3		noel 3468	. . . . . . . . 9 |- -. x e. (/)
4	3	intnan 931	. . . . . . . 8 |- -. ( -. A = 1o /\ x e. (/) )
5	4	biorfi 748	. . . . . . 7 |- ( ( A = 1o /\ x e. 1o ) <-> ( ( A = 1o /\ x e. 1o ) \/ ( -. A = 1o /\ x e. (/) ) ) )
6	2, 5	bitr4i 187	. . . . . 6 |- ( x e. if ( A = 1o , 1o , (/) ) <-> ( A = 1o /\ x e. 1o ) )
7	1, 6	sylib 122	. . . . 5 |- ( ( A e. ~P 1o /\ x e. if ( A = 1o , 1o , (/) ) ) -> ( A = 1o /\ x e. 1o ) )
8	7	simprd 114	. . . 4 |- ( ( A e. ~P 1o /\ x e. if ( A = 1o , 1o , (/) ) ) -> x e. 1o )
9	7	simpld 112	. . . 4 |- ( ( A e. ~P 1o /\ x e. if ( A = 1o , 1o , (/) ) ) -> A = 1o )
10	8, 9	eleqtrrd 2286	. . 3 |- ( ( A e. ~P 1o /\ x e. if ( A = 1o , 1o , (/) ) ) -> x e. A )
11		elex2 2790	. . . . 5 |- ( x e. A -> E. y y e. A )
12		pw1m 7355	. . . . 5 |- ( ( A e. ~P 1o /\ E. y y e. A ) -> A = 1o )
13	11, 12	sylan2 286	. . . 4 |- ( ( A e. ~P 1o /\ x e. A ) -> A = 1o )
14		simpr 110	. . . . 5 |- ( ( A e. ~P 1o /\ x e. A ) -> x e. A )
15	14, 13	eleqtrd 2285	. . . 4 |- ( ( A e. ~P 1o /\ x e. A ) -> x e. 1o )
16	13, 15, 6	sylanbrc 417	. . 3 |- ( ( A e. ~P 1o /\ x e. A ) -> x e. if ( A = 1o , 1o , (/) ) )
17	10, 16	impbida 596	. 2 |- ( A e. ~P 1o -> ( x e. if ( A = 1o , 1o , (/) ) <-> x e. A ) )
18	17	eqrdv 2204	1 |- ( A e. ~P 1o -> if ( A = 1o , 1o , (/) ) = A )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 104   \/ wo 710   = wceq 1373   E.wex 1516   e. wcel 2177   (/)c0 3464   ifcif 3575   ~Pcpw 3621   1oc1o 6508

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-io 711  ax-5 1471  ax-7 1472  ax-gen 1473  ax-ie1 1517  ax-ie2 1518  ax-8 1528  ax-10 1529  ax-11 1530  ax-i12 1531  ax-bndl 1533  ax-4 1534  ax-17 1550  ax-i9 1554  ax-ial 1558  ax-i5r 1559  ax-ext 2188

This theorem depends on definitions:  df-bi 117  df-tru 1376  df-nf 1485  df-sb 1787  df-clab 2193  df-cleq 2199  df-clel 2202  df-nfc 2338  df-v 2775  df-dif 3172  df-un 3174  df-in 3176  df-ss 3183  df-nul 3465  df-if 3576  df-pw 3623  df-sn 3644  df-suc 4426  df-1o 6515

This theorem is referenced by:  pw1map  16073