CS40 HW1 Solution
August 10, 2009
Grading Policy
1. 2 points for each small question from #1 to #7 and #9. 10 points for the proof of
#8.
2. 8 points for clearance.
3. totally 100 pts.
1
Section 1.1 problem 18, 14 points
a) The necessary condition is the conclusion: If you get promoted, then you wash
the boss’s car.
b) If the winds are from the south, then there will be a spring thaw.
c) The sufﬁcient condition is the hypothesis: If you bought the computer less than
a year ago, then the warranty is good.
d) If Willy cheats, then he gets caught.
e) The "only if" condition is the conclusion: If you access the website, then you
must pay a subscription fee.
f) If you know the right people, then you will be elected.
g) If Carol is on a boat, then she gets seasick.
2
Section 1.1 problem 28, 12 pts
a) and b)
p
¬
p
p
→ ¬
p
p
↔ ¬
p
T
F
F
F
F
T
T
F
DNF of a):
¬
p
c) and d)
p
q
···
p
⊕
(
p
∨
q
)
(
p
∧
q
)
→
(
p
∨
q
)
T
T
···
F
T
T
F
···
F
T
F
T
···
T
T
F
F
···
F
T
1
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 Fall '09
 Egiceoclu
 carol, Disjunctive syllogism, CS course

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