Theorem frege54cor1b

Description: Reflexive equality. (Contributed by RP, 24-Dec-2019)

	Ref	Expression
Assertion	frege54cor1b	$$⊢\left[x/y\right]y=x$$

Proof

Step	Hyp	Ref	Expression
1		equsb1	$$⊢\left[x/y\right]y=x$$