Theorem aecoms

Description: A commutation rule for identical variable specifiers. Usage of this theorem is discouraged because it depends on ax-13 . (Contributed by NM, 10-May-1993) (New usage is discouraged.)

	Ref	Expression
Hypothesis	aecoms.1	⊢ ( ∀ 𝑥 𝑥 = 𝑦 → 𝜑 )
Assertion	aecoms	⊢ ( ∀ 𝑦 𝑦 = 𝑥 → 𝜑 )

Proof

Step	Hyp	Ref	Expression
1		aecoms.1	⊢ ( ∀ 𝑥 𝑥 = 𝑦 → 𝜑 )
2		aecom	⊢ ( ∀ 𝑦 𝑦 = 𝑥 ↔ ∀ 𝑥 𝑥 = 𝑦 )
3	2 1	sylbi	⊢ ( ∀ 𝑦 𝑦 = 𝑥 → 𝜑 )