Proofs II, #10
derive (R v T)
1.
(
P & Q
)
⊃
R
premise
2.
(
S & R
)
⊃
T
premise
3.
P & S
prem
4.
Q v R
prem
5.
P
⊃
(Q
⊃
R)
exp, 1
6.
S
⊃
(R
⊃
T)
exp. 2
7.
P
simp, 3
8.
S
simp, 3
9.
Q
⊃
R
mp, 5,7
10.
R
⊃
T
mp, 6,8
11.
R v T
dil, 4,9,10