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Diffstat (limited to 'examples/systemS/ex2eng.txt')
| -rw-r--r-- | examples/systemS/ex2eng.txt | 7 |
1 files changed, 0 insertions, 7 deletions
diff --git a/examples/systemS/ex2eng.txt b/examples/systemS/ex2eng.txt deleted file mode 100644 index f1ef836ae..000000000 --- a/examples/systemS/ex2eng.txt +++ /dev/null @@ -1,7 +0,0 @@ -Suppose A -> B. We will show that ~ B -> ~ A. -It is enough to assume A -> B, ~ B and show ~ A. -Thus, by rewriting ~ A we may assume A -> B, ~ B and show A -> _|_. -It is enough to assume A, A -> B, ~ B and show _|_. -Then, by Modus ponens, we get A, A -> B, B, ~ B to prove _|_. -In particular we get B, ~ B to prove _|_. -Hence we get _|_ as desired. |