Theorem ichid 44903

Description: A setvar variable is always interchangeable with itself. (Contributed by AV, 29-Jul-2023.)

Assertion

Ref	Expression
ichid	⊢ [𝑥⇄𝑥]𝜑

Proof of Theorem ichid

Dummy variable 𝑎 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		sbid 2248	. . . . 5 ⊢ ([𝑥 / 𝑥][𝑎 / 𝑥]𝜑 ↔ [𝑎 / 𝑥]𝜑)
2	1	sbbii 2079	. . . 4 ⊢ ([𝑥 / 𝑎][𝑥 / 𝑥][𝑎 / 𝑥]𝜑 ↔ [𝑥 / 𝑎][𝑎 / 𝑥]𝜑)
3		sbid2vw 2251	. . . 4 ⊢ ([𝑥 / 𝑎][𝑎 / 𝑥]𝜑 ↔ 𝜑)
4	2, 3	bitri 274	. . 3 ⊢ ([𝑥 / 𝑎][𝑥 / 𝑥][𝑎 / 𝑥]𝜑 ↔ 𝜑)
5	4	gen2 1799	. 2 ⊢ ∀𝑥∀𝑥([𝑥 / 𝑎][𝑥 / 𝑥][𝑎 / 𝑥]𝜑 ↔ 𝜑)
6		df-ich 44898	. 2 ⊢ ([𝑥⇄𝑥]𝜑 ↔ ∀𝑥∀𝑥([𝑥 / 𝑎][𝑥 / 𝑥][𝑎 / 𝑥]𝜑 ↔ 𝜑))
7	5, 6	mpbir 230	1 ⊢ [𝑥⇄𝑥]𝜑

Syntax hints:   ↔ wb 205  ∀wal 1537  [wsb 2067  [wich 44897

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1913  ax-6 1971  ax-7 2011  ax-12 2171

This theorem depends on definitions:  df-bi 206  df-an 397  df-ex 1783  df-sb 2068  df-ich 44898

This theorem is referenced by:  icheqid  44913