1.
2.
3.
/S
See also:
Implication
Formal Proof
Well Formed
Validity
ds
+
(A & B)
(~D + S)
D
~(A & B)
4.
1,3 DS
1. Find a disjunctive statement.
2. Pick out the left component.
3. Scan lines to find a negation of the left component.
4. Append line showing you derived the right component of line 1 by DS from lines 1 and 3.