Theorem bj-issettru

Description: Weak version of isset without ax-ext . (Contributed by BJ, 24-Apr-2024) (Proof modification is discouraged.)

	Ref	Expression
Assertion	bj-issettru	$$⊢\exists xx=A\leftrightarrow A\in \left\{y|\top \right\}$$

Proof

Step	Hyp	Ref	Expression
1		bj-denotes	$$⊢\exists xx=A\leftrightarrow \exists zz=A$$
2		bj-denoteslem	$$⊢\exists zz=A\leftrightarrow A\in \left\{y|\top \right\}$$
3	1 2	bitri	$$⊢\exists xx=A\leftrightarrow A\in \left\{y|\top \right\}$$