Theorem equcom

Description: Commutative law for equality. Equality is a symmetric relation. (Contributed by NM, 20-Aug-1993)

	Ref	Expression
Assertion	equcom	$$⊢x=y\leftrightarrow y=x$$

Proof

Step	Hyp	Ref	Expression
1		equcomi	$$⊢x=y\to y=x$$
2		equcomi	$$⊢y=x\to x=y$$
3	1 2	impbii	$$⊢x=y\leftrightarrow y=x$$