Theorem csb0OLD

Description: Obsolete version of csb0 as of 28-Jun-2024. (Contributed by NM, 18-Aug-2018) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	csb0OLD	$$⊢⦋A/x⦌\varnothing =\varnothing$$

Proof

Step	Hyp	Ref	Expression
1		csbconstg	$$⊢A\in \mathrm{V}\to ⦋A/x⦌\varnothing =\varnothing$$
2		csbprc	$$⊢\neg A\in \mathrm{V}\to ⦋A/x⦌\varnothing =\varnothing$$
3	1 2	pm2.61i	$$⊢⦋A/x⦌\varnothing =\varnothing$$