DISCRETE MATHEMATICS
SPRING 2018
HULSEN
PROJECT 2
Part A is Practice for Set 2 concepts, and will also help as we approach Test 2.
Part B is Exploration, into further required topics in Discrete Math.
These will not be part of Test 2.
On separate paper, write your solutions to the problems neatly,
well-organized and with ALL work shown.
Each question is worth 5 points, unless otherwise noted.
Part A = 90 points; Part B = 10 points
PROJECT 2 is not a group project. Everyone must hand in their own project.
Make sure you attach a COVER SHEET:
Your name, course, instructor name, semester, project name.
DUE:
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PART A: SET 2 PRACTICE
1. Write the truth table for:
¬ (𝑝˄𝑞) ˅ (𝑟˄¬𝑝)
2. Using: p: Today is Monday.
q: It is rainy.
r: It is hot.
(a-c below) Write the English translation for:
a. ¬𝑝 → (𝑞 ˅ 𝑟)
b. ¬ (𝑝 ˅ 𝑞 ) ↔ 𝑟
c. ( p ˄ (q ˅ r )) → ( r ˅ ( q ˅ p ))
(d-e below) Write the following sentences using p, q, r, above, and logical connectives
(logical operators):
d. “It is rainy and hot, but today is not Monday.”
e. “It is not hot, but it is rainy or today is Monday.”
3.
Prove the following, using logical equivalences. For each step, state the name of the
logical equivalence or property you used.
¬ [ (¬𝑝 ˄ 𝑞) ˅ (¬𝑝 ˄ ¬𝑞)] ˅ (𝑝˄𝑞) ≡ 𝑝
4. Use a truth table to prove:
𝑝 ⊕ 𝑞 ≡ (𝑝˄¬𝑞) ˅ (¬𝑝 ˄ 𝑞)
5. In our textbook, use pg. 55 #34 a - d, but do the following for each:
* Write statements as needed to form the given propositions. Assign variables (p, q or as
appropriate) for the statements. Write the variable along with the statement you have
assigned to it.
* Write the proposition using quantifier notation and the variables you have assigned for
the statements.
* Write the negation of the proposition in English.
* Write the negation of the proposition, this time using quantifier notation, and the
variables you have assigned for the statements.
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6. (10 points)
For each statement below (a – f), do the following:
*Write the statement using quantifier notation and mathematical symbols;
*Determine the truth value of the statement, AND explain/show how you determined the
truth value. Show counterexamples, or examples as needed.
a. For every x, for every y, x2 < y + 1
b. For every x, for some y, x2 < y + 1
c. For some x, for every y, x2 < y + 1
d. For some x, for some y, x2 < y + 1
e. For some y, for every x, x2 < y + 1
f. For every y, for some x, x2 < y + 1
7. Given:
p: Fishing is a popular sport.
q: Curling is popular in New Jersey.
For the following arguments (a – c), do the following:
* Write the argument symbolically.
* State which rule of inference is used.
a. Fishing is a popular sport. Therefore, fishing is a popular sport or curling is popular in
New Jersey.
b. If fishing is a popular sport, then curling is popular in New Jersey. Fishing is a popular
sport. Therefore, curling is popular in New Jersey.
c. Fishing is a popular sport or curling is popular in New Jersey. Curling is not popular in
New Jersey. Therefore, fishing is a popular sport.
8. (10 points)
Prove that if n is an integer, and 3n+2 is even, then n is even.
a. Prove using a direct proof.
b. Prove using proof by contraposition.
c. Prove using proof by contradiction.
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9. Use proof by cases (hint: 3 cases) to prove if n is an integer, then n2 ≥ n.
10. (10 points)
Use mathematical induction to prove the following, for all positive integers n. Show ALL
algebraic steps!
1
1
1
1
𝑛
+
+
+⋯+
=
(2𝑛 − 1)(2𝑛 + 1)
1∙3
3∙5 5∙7
2𝑛 + 1
11. (10 points)
Use mathematical induction to prove that n3 + 2n is divisible by 3, where n is a nonnegative
integer. Show ALL algebraic steps!
12. In Section 2.4, we learned about recurrence relations. Section 5.3 addresses recursion.
Explain how these are related. (Only 1 – 2 paragraphs maximum.)
13. On page 357, do # 4a, and #4c.
14. Give a recursive definition for the sequence an , where n = 1, 2, 3, … if
an = 4n – 2
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EXTRA CREDIT
15. On page 358, do # 28 a, b, c
EXTRA CREDIT
16. Use proof by cases to show that:
Every integer that is a perfect cube is:
* a multiple of 9;
* or is one more than a multiple of 9;
* or is one less than a multiple of 9.
EXTRA CREDIT
17. Prove that if n is an integer, then (the symbols below are “floor”):
𝑛
⌊2⌋ =
𝑛
⌊2⌋ =
𝑛
if n is even, and
2
𝑛−1
2
if n is odd.
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PART B: EXPLORATION
ALGORITHMS, BIG-O, BIG-THETA, BIG-OMEGA
Algorithms are covered in depth in computer science classes. Most discrete mathematics classes
cover a few algorithm-related topics. READ pgs. 191 – 193.
1. On pg. 196, 197 (note example at top of pg 197) , read about the “bubble sort” algorithm.
On pg. 203, above problem #41, read about “selection sort” algorithm. But also see the
YouTube video “Sorting Algorithm | Selection Sort step by step guide”.
Apply the bubble sort AND selection sort method to the list below. Write each step /
iteration of the list until the entire list is sorted.
List: 5, 3, 1 ,6 ,2, 4
Big-O, Big-Theta and Big-Omega…no I am not making this up! ;-) .. are methods to estimate the
growth of functions or algorithms, based on the complexity of the function or algorithm.
Complexity theory is a topic in advanced computer science courses.
Big-O: READ pgs. 204 – 211. Make note of the graph on pg. 211.
Big-Theta, Big-Omega: READ pgs. 214 – 216.
2. On pg. 216, do problem # 26, parts a, b, c, for Big-O.
3. EXTRA CREDIT: do problem #26 above, for Big-Theta and Big-Omega.
4. EXTRA CREDIT: Read about little-o on pg. 218. See problem #61. DO NOT use the
examples from # 61, but make up three of your own examples for little-o, and solve them.
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