>dford
Theorem.
Arguments:
(pr),
(pr),
(pr),
Hypotheses:
(
(
))
Assertions:
(
(
))
Proof:
Hyp
Ref
Line
Expr
Hypo
1
(
(
))
df-or
2
((
)
(
))
1, 2
brpi22<
3
(
(
))