Theorem trujust

Description: Soundness justification theorem for df-tru . Instance of monothetic . (Contributed by Mario Carneiro, 17-Nov-2013) (Revised by NM, 11-Jul-2019)

	Ref	Expression
Assertion	trujust	$$⊢\left(\forall xx=x\to \forall xx=x\right)\leftrightarrow \left(\forall yy=y\to \forall yy=y\right)$$

Proof

Step	Hyp	Ref	Expression
1		monothetic	$$⊢\left(\forall xx=x\to \forall xx=x\right)\leftrightarrow \left(\forall yy=y\to \forall yy=y\right)$$