Theorem tbtru

Description: A proposition is equivalent to itself being equivalent to T. . (Contributed by Anthony Hart, 14-Aug-2011)

	Ref	Expression
Assertion	tbtru	$$⊢\phi \leftrightarrow \left(\phi \leftrightarrow \top \right)$$

Proof

Step	Hyp	Ref	Expression
1		tru	$$⊢\top$$
2	1	tbt	$$⊢\phi \leftrightarrow \left(\phi \leftrightarrow \top \right)$$