>>581
LJで#2と#5。

------(I)
Q |- Q
---------(WL)
Q, P |- Q
---------(PL)
P, Q |- Q
-----------(~L)
P, Q, ~Q |-
-----------(PL)
P, ~Q, Q |-
-------------(WR)
P, ~Q, Q |- R
---------------(->R)
P, ~Q |- Q -> R
-----------------------------(\/R2)
P, ~Q |- (P -> Q) \/ (Q -> R)
---------------------------------(~L)
P, ~Q, ~((P -> Q) \/ (Q -> R)) |-
---------------------------------(PL)
P, ~((P -> Q) \/ (Q -> R)), ~Q |-
---------------------------------(~R)
P, ~((P -> Q) \/ (Q -> R)) |- ~~Q
---------------------------------(PL) ------(I)
~((P -> Q) \/ (Q -> R)), P |- ~~Q　 　 Q |- Q
--------------------------------------------(->L)
（続く）