Homework Assignments
MAP 2302, Sections 3227 & 3615 -- Elementary Differential Equations
Fall 2006


Last update made by D. Groisser Fri Dec 8 19:51:37 EST 2006

Homework problems and due dates (not the dates the problems are assigned) are listed below. This list, especially the due dates, will be updated frequently, usually in the late afternoon or evening the day of class or the next morning. Due dates and assignments more than one lecture ahead are estimates; in particular, due dates may be moved either forward or back, and problems not currently on the list from a given may be added later (but prior to their due dates, of course). On a given day there may be problems due from more than one section of the book.

Exam-dates and some miscellaneous items may also appear below.

If one day's assignment seems lighter than average, it's a good idea to read ahead and start doing the next assignment, which may be longer than average.

Unless otherwise indicated, problems are from our textbook (Nagle, Saff, & Snider, 4th edition). It is intentional that some of the problems assigned do not have answers in the back of the book or solutions in a manual. An important part of learning mathematics is learning how to figure out by yourself whether your answers are correct.

Read the corresponding section of the book before working the problems. Don't just read the examples, and don't just try the homework problems and refer to the text only if you get stuck.


Date due Section # / problem #'s
F 8/25/06
Read the syllabus and the web handouts "Taking notes in a college math class" and "What is a solution?", obtainable from the Web.

Read Section 1.1 and do problems 1.1/ 1-16. We did not get to "order" or "linear vs. non-linear" in class on Wednesday, but you should have no trouble doing these problems based on pp. 4-5 of the book, and I will review this material on Friday. Also, do non-book problem #1. Note: if you have a problem viewing any of my PDF files, check your version of Adobe Acrobat at http://www.adobe.com/products/acrobat/ . You may need to update (all you need is a recent version of the free Adobe Reader).


M 8/28/06
1.2/ 1, 3-5, 14, 15, 19.
W 8/30/06
  • 1.2/ 2, 10, 11, 30.

  • Do non-book problem #2.

  • Read pp. 12-14.

  • Read sections 2.1 and 2.2. In your reading, make sure you understand the discussion following Example 3 (bottom of p. 44 to top of p. 45).
  • F 9/1/06
  • 1.2/18, 23-29
  • 2.2/1-5 (you should be able to do these just based on your reading that was due Wednesday)

    I'm about one lecture behind where I'd hoped to be. I would suggest re-reading Section 2.2 and trying start on the assignment due Wednesday 9/6/06. You may be able to do them based just on your reading, and you will then have a smaller assignment over the weekend.


  • Every Friday
    Homework discussion: Starting 9/1/06, I will hold a weekly session on Friday, 9th period, in Little 125, for the purposes of answering homework questions for recently assigned homework--problems that were due that week, or, if a week was skipped, since the last homework-discussion. I will continue holding this session only as long as at least 10 students show up; I will discontinue it the second time that fewer than 10 show up. (For the purposes of this two-strikes-and-you're-out policy, today, 9/1/06, does not count, since I did not get a room and put out this announcement till today.) I stress again that I expect you to be doing all your homework by the due-dates, and that these homework sessions are intended for recent homework problems, not to help you catch up the week before an exam. If I cancel the sessions because there's insufficient interest (i.e. fewer than 10 attendees) when an exam is not imminent, I will not re-institute them the week before an exam.
    W 9/6/06
    2.2/ 8, 9, 11, 13, 17, 18, 23, 27abc, 29-34. "Solve the equation" means "find the general solution of the equation" (i.e. find all solutions). For some of the problems in the "7-16" group, the method I presented in class is not sufficient to find all the solutions, so you may not be able to finish these problems completely yet. Problem 30 of this assignment illustrates the relevant issue, but on Wednesday we will see how to find systematically the solutions that are missed by separating variables (these correspond to "Case (ii)" of the analysis I started on Friday but did not complete). Save your work on this assignment so that in the next assignment, you can fill in any solutions you missed on this assignment.
    F 9/8/06
  • Go back and check whether your general solutions, in the problems from the previous assignment that asked for them, omitted any equilibrium solutions. In any future problems involving separable equations, when you're asked to find the general solution, make sure that you have indeed included all solutions (both non-equilibrium and equilibrium).

  • 2.2/6, 16, 22

  • Read Section 2.3.

  • 2.3/1-6. If you feel comfortable with the method, try some of the problems due Monday. The ones I would start with are numbers 7, 23 (read Example 2 on p. 52 first), 24, and 28.
  • M 9/11/06
    2.3/7, 8, 13-15, 17-20, 23 (read Example 2 on p. 52 first), 24, 27a, 28.
    Special note about Friday's problem-session
    For those of you who attended the problem-session on Friday 9/8/06: I incorrectly wrote a formula (part of the general solution to some DE) as 1/(Cet+1). What I should have written was 1/(Ce-t+1).
    W 9/13/06
  • 2.3/30-33, 35. In #33, note that what you might think is only a minor difference between the DE's in parts (a) and (b)--a sign-change in just one term--drastically changes the nature of the solutions. When solving differential equations, a tiny algebra slip can make your solutions utter garbage. For this reason there is usually no such thing as a "minor algebra error" in solving differential equations.

  • Read Section 2.4. If you think you understand the method of solving exact equations well enough, get started on the problems that are due Friday. The best ones to start with are numbers 1-8, 27a, and 28a.
  • F 9/15/06
  • 2.4/1-8.
  • Based on your reading (especially the Test for Exactness on p. 61, the Method for Solving Exact Equations on p. 63, and Examples 2 and 3), try to solve 2.4/11, 12, 16, 17, 19, 20-22, 27a, 28a, 32 (note that #22 is the same DE as #16, so you don't have to solve a new DE, you just have to incorporate the initial condition into your old solution). I will be carefully going over this method in class, with examples, on Friday, so it's okay to wait until Friday after class to start these problems; they're really due Monday. But the more you're able to get done by Friday, the more time you'll have to familiarize yourself with this method and to review other material before Wednesday's exam.

  • Note: sometimes the simple algebraic operation of clearing fractions can turn a non-exact equation into an exact one (cf. Example 1, p. 59). You are responsible for being able to solve such equations.
  • Special note
    Exam-date change: first midterm is postponed until Wednesday, Sept. 20. This may result in other exam-dates being postponed. I'll update you when we get closer to the originally-estimated dates.
    M 9/18/06
  • Complete all the problems from Section 2.4 listed above that you haven't completed yet.

  • Read the online handout "A terrible method for solving exact equations". This year, the parenthetical "we proved it!" on the handout does not apply, since I didn't get to the proof in class. However, you did read the proof in the book as part of your homework.
  • Special note
    Here is what I told a 2003 Differential Equations class after they performed less well than they'd hoped on their first midterm. I'm hoping that this advance warning will help you to avoid the flaws in their study habits, exam prep, etc.
    If you had any unpleasant surprises on [this] exam, please re-read the section on prerequisites on the class home page, and the sections on homework, workload, attendance, and miscellany on the syllabus. You may also want to re-read the handout "Taking notes in a college math class".

    Never try to figure out the minimum amount of work you need to do to get the grade you want. Your goal should be to put yourself in a position to get 100% on every exam, regardless of what subset of fair-game material ends up being represented on the exam, and regardless of what form the questions take. If you make this your goal, you will learn and retain far more material, and get far better grades.


    W 9/20/06
    First mid-term exam (assignment is to study for it). The relevant book-sections for the exam are 1.1-1.2 and 2.1-2.4. However, bear in mind that I went into greater depth than the book on certain topics, and anything that I covered in class or was covered in the book or in homework is fair game for the exam.
    F 9/22/06
    Read Sections 4.1 and 4.2.
    M 9/25/06
    4.1/1-10. Typo correction: In #10a, 2nd line, the function written after "B" should be "sin", not "cos".
    W 9/27/06
  • Review your notes.
  • Catch up and/or get ahead in your homework for other classes, so that you'll have time for MAP2302 problems once I start assigning them again next lecture.
  • F 9/29/06
  • Check that all the operators listed on the table in Monday's class are linear except for the squaring operator.
  • Do non-book problems 3-6.
  • M 10/2/06
    Re-read section 4.2 and do problems 4.2/1-10, 13, 14, 17, 18, 20, 21, 22, 26.

    Exam 1 is now graded! For the grade-scale, click on your section: 6th period (12:50 - 1:40) or 8th period (3:00 - 3:50). The linked page "list of scores" has some grade-related statistics.
    Exams will be returned at the end of class on Monday (or, if you want to get yours earlier, you may come to my Monday 10:30-11:30 office hour). This is the only day I will bring your exam to class. If you are absent Monday, you will have to see me in office hours to get your exam back. Any exams not picked up after one week may be thrown out. I will give no grade-related information by email, and will not respond to email asking for such information or attempting to engage me in a grade-related discussion. I will discuss grades, grading, and grade policy only in person.


    W 10/4/06
  • 4.2/ 27-33, 39, 40. Typo correction: #39 has a typo in line 5. The function multiplying c2 should be y3(t).

  • Read Section 4.3.
  • M 10/9/06
  • 4.3/1, 4, 6, 7, 9-12, 17, 18, 28, 30, 38, 39
  • Do non-book problem 7.
  • W 10/11/05
  • Perform the check that I assigned in class for homework: that if c is a complex constant and h is a complex-valued function, then (ch)'=ch'.

  • Read section 4.5 pp. 186-189 through the end of Example 2, excluding Example 1. We will cover section 4.4 after we have done most or all of section 4.5 , but most of the examples in 4.5 assume (naturally) that you've already read 4.4; except for Example 2 they will not make sense to you yet.

  • 4.5/1-8.

  • I discovered some typographical errors in the book problems. See the assignments for 9/25/06 and 10/4/06 for the corrections.
  • F 10/13/06
    Read Section 4.4. If possible, get started on the next assignment, which is pretty long. I've broken it into pieces in the order in which you should attempt it; depending on how far I get Friday, I may spread it across more than one assignment.
    M 10/16/06
  • 4.4/1-8, 9-11, 14, 17. Hint for #9: 9=9e0x (same idea applies to #10). Hint for #14: 2=eln(2).
  • Based on your reading, try to do as many problems as possible from the assignment due Wednesday 10/18, so that this material will be less new to you when you study for the midterm.
  • Special note
    Date for 2nd midterm: Friday, Oct. 20. Fair game for the exam is anything in sections 4.1-4.5, plus material covered in class since the last exam that's not in the book.
    W 10/18/06
  • 4.4/12, 13, 15, 16, 18, 20-24, 27-32
  • Finish reading Section 4.5.
  • 4.5/9-16, 17, 18, 20, 22, 23-30, 31-36. (READ INSTRUCTIONS--problems 9-16 require no significant computation!) The box on p. 191, "Method of Undetermined Coefficients (Revisited)" covers all the different types of functions g for which L[y]=g can be solved by this method; from your reading and from this box, you should be able to do most or all of the problems from Section 4.5 even before Wednesday's lecture.
  • F 9/20/06
    Second mid-term exam (assignment is to study for it).
    M 10/23/06
    No homework.
    W 10/25/06
  • Read Sections 6.1 and 6.2.
  • 6.2/15-18.
  • F 10/27/06
  • Read Section 6.3. Note that the book's operator (D-α)22 is the same as the operator (D-(α+βi))(D-(α-βi)) that I used in class (check this).

  • 6.3/1-4, 11-20, 21-29. Although the book says to use the method of undetermined coefficients for problems 1-4 and the annihilator method for problems 21-29, they are really the same method, so it's OK to use the method of undetermined coefficients for all these problems. The DE in #29 is third-order, but you should have no problem factoring the characteristic polynomial.
  • Exam 2 is now graded. For the grade-scale, click on your section: 6th period (12:50 - 1:40) or 8th period (3:00 - 3:50).


    M 10/30/06
    4.6/1-18, 19 (first sentence only), 21, 25
    Special Notice

    Exam-date change. The third midterm will not be given on the originally-planned date of Nov. 8. It will be given either on Wed. Nov. 15 or Fri. Nov. 17. I will announce the exact date when I'm sure of it. In either case, my intention is to return the graded exams to you by Mon. Nov. 20, the last date to drop a class.


    W 11/1/06
  • Read sections 7.1 and 7.2.
  • 7.2/21-28.
  • BOO!
  • F 11/3/06
    7.2/1-8, 10, 12 (note: "Use Definition 1" means "Use Definition 1", NOT the box on p. 358 or any other table of Laplace Transforms), 13-20, 29a-d,f,g,j.
    M 11/6/06
    7.3/1-8,12,14,19,31
    W 11/8/06
  • 7.3/9,10,25
  • Read the review of partial fractions in Section 7.4 (pp. 370--373). I will not have time to review this prerequisite Calc 2 material in class, so it is important that you come to class prepared to follow any problem I present that uses partial fractions without asking the sort of questions one would expect from students who have never seen (or have completely forgotten) partial fractions.
  • 7.4/1-10, 15, 16, 20.
  • M 11/13/06
  • 7.4/21-24, 26, 27.
  • Read the web handout "Partial fractions and Laplace Transform problems" (pdf file).
  • 7.5/1-8,10, 15,21,22,29.
  • Read Section 7.6 through Example 6.
  • Special note
    Date for 3rd midterm: Friday, Nov. 17.
    W 11/15/06
    7.6/1-18
    F 11/17/06
    Third mid-term exam (assignment is to study for it). Although I've already had you read through Example 6 in Section 7.6, the exam will not cover any material beyond Example 4. You will be tested on transforms and inverse-transforms involving piecewise-continuous functions that are discontinuous and/or "piecewise-defined", but you will not be required to solve any DE's where the right-hand side is such a function (such as in Example 5 of Section 7.6). As usual, everything else is fair game: anything in Section 4.6, anything in Chapter 7 through Example 4 of Section 7.6, anything covered in homework, and anything covered in class. Every problem on the Laplace-transform sample exam is of fair-game type except for 5b.
    M 11/20/06
    Read Section 7.8. We will cover Section 7.7 after Section 7.8.
    W 11/22/06
    There will be class this day. The day before a holiday is not a holiday. 7.6/21-28, 29-31, 33, 35-37, 39
    M 11/27/06
  • Read Sections 8.1 and 8.2. These are a review of Calc 2 material; I will only discuss them briefly, if at all, in class, but I will expect you to have this material at your fingertips.
  • Eat.
  • Have fun and think a lot about differential equations. Oh, excuse me, I'm being redundant.
  • W 11/29/06
  • 7.8/1-12, 13-15, 17-19, 21-23, 30
  • 7.7/6,9,13, 15, 20
  • F 12/1/06
  • 7.7/1-4
  • 8.1/1,2,4,8-12. I will not spend time in class to cover Section 8.1; you should be able to do all these problems based on the previously-assigned reading. On Friday I will rapidly review Section 8.2 and begin to discuss Section 8.3.

    Note: This week my Friday morning office-hour is cancelled so that I may attend a UF Board of Trustees meeting. However, I will hold our Friday 9th-period problem-discussion session (in Little 125, as usual).


  • M 12/4/06
  • 8.2/1-6 (find only the open interval of convergence; don't worry about the endpoints),7-10,17,19,21,22,23,24,27, 31,34,37,38 (better hint: integrate the series for 1/(1+x) and figure out what to do next).
  • Read Sections 8.3 and 8.4. When I test you on Section 8.4, I will be more concerned with your knowing how to find power-series solutions than with knowing what Theorem 5 says about their radii of convergence.
  • 8.3/1,3,5,7-10.
  • W 12/6/06
  • 8.3/11-14,18, 20-22,24,25,32-34
  • 8.4/15, 20,21,23,25, 29 (in #29 be careful not to use the letter n as a summation index since it already has an assigned, different meaning in this problem).
  • Material for final exam
    The final will be cumulative, with a disproportionate emphasis on material covered since the last midterm (probably more than 25% but less than 50%).
  • Sections 1.1-1.2, 2.1-2.4, 4.1-4.6, 6.2-6.3, 7.1-7.8 (minus the portion of 7.6 from Example 7 to the end of the section), 8.1-8.3, and the material from 8.4indicated below.
  • Section 8.4: you are not responsible for the material in this section on radius of convergence. Basically this means that what you are responsible for in this section is the first two sentences of Theorem 5 and everything from Example 4 to the end of the section. For exam-problems related to this section, I would only ask you to deal with power series centered at 0 (i.e. with x0 = 0).
  • Anything covered in homework, both book- and non-book problems.
  • Anything I said in class, whether or not it was covered in the book or in homework.
  • Review session
    and
    remaining office hours

    I will hold a question-and-answer review session (6th- and 8th-period sections combined) on Friday Dec. 8, starting at 12:50, in our usual classroom. I may be a few minutes late. I'm expecting the session to last an hour, but it could be longer or shorter depending on the questions asked.
  • My office hour on Friday Dec. 8 is cancelled.
  • For students who have been attending class regularly, I will hold the office hours listed below. For students who have not been attending class regularly, I have no more office hours for the rest of the semester. The hours on Tues., Wed., and Thurs. of next week are only for students who have their exam on Friday, and are tentative until Monday 12/11 (they may change if students tell me they can't make those hours, but I won't change them after Monday, and I won't make exceptions for students who haven't told me by Monday that they have conflicts with all the hours listed below).
    • Mon. 12/11, 10:30-11:30 (shared with students needing to see me for academic advising) and
      2:00-3:00 (my MAP 2302 students only).

      Update: My Monday 10:30-11:30 hour is completely booked with advising-appointments. Unless your MAP2302 exam is Tuesday and you cannot make my Monday 2:00-3:00 hour on Monday, please do not come to my 10:30-11:30 hour.

    • Tues. 12/12, 2:00-3:00 (shared with students needing to see me for academic advising, but I will stay later if necessary to answer your questions)
    • Wed. 12/13, 11:00-12:00 and 2:00-3:00.
    • Thurs. 12/14: 2:00-3:00.

    Please remember that I will not communicate any grade-related information by email; email that asks grade-related questions will not receive responses. Students wishing to know their final-exam scores and/or wanting to see their graded finals should see me in my office in January.



  • Class home page