bi<

Theorem.

Arguments:

(pr), (pr),

Assertions:

(()())

Proof:

Hyp	Ref	Line	Expr
	df-bi	1	((()(()()))((()())()))
1	pm3.26im	2	(()(()()))
	pm3.27im	3	((()())())
2, 3	syl	4	(()())