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1
FIRST MIDTERM INFORMATION
TEST GIVEN 1/25/10
1. A tautology is a statement form which is true under any
truth assignment to its variables. A contradiction is a
statement form which is false under any truth assignment to
its variables. Two statement forms are logically equivalent
if and only if they have the same truth values under any
truth assignment to the variables that appear.
The most common scores for this problem were 8 and 10. The
most common error is to not mention variables or truth
assignments.
2. Straightforward construction of truth table. Some people
made an error in the truth table and answered "neither". I
gave 0 for that. If you answered correctly, but I spotted a
defect in the truth table, then there was a few points
taken off.
3. Same comments as 2. A few points taken off for not
clearly identifying the critical rows.
4. (
∀
x
∈
Z)(~x < x).
(
∀
x
∈
Z)(x > 1
→
x > 0).
(
∃
x
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 Fall '08
 JOSHUA
 Math

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