Math 2280-1
Introduction to
Differential Equations
Spring term, 2006

Homework Assignments

Send e-mail to : Professor Korevaar

Links:
Math 2280 home page
Professor Korevaar's home page
Department of Mathematics



Homework is generally due each Friday at the start of class, and solutions should be posted by the following Monday. The most recent assignments are listed first. Underlined problems are to be handed in, the remaining ones are optional.

Due Wednesday, April 26: Last assignment; Hurray!
     9.5   1, 7, 13, 15, 16;
     9.6   1, 4, 5, 11, 17, 21.
   solutions15.pdf
   Grading: 26 points, distributed as follows:
     9.5:   1, 7 = 2 points each; 13abc = 2 points each; 15 = 3 points.
     9.6:   1, 4, 5 = 2 points each; 11 = 3 points; 21ab = 2 points each (21cd not graded).

Due Friday, April 21:
     9.1   3, 6, 7, 10, 12, 13, 15, 17, 20, 27, 28, 29, 30;
     9.2   2, 9;
     9.3   1, 9, 17, 19, 20;
     9.4   1, 7, 9, 13.
   solutions14.pdf
   Grading: 34 points, distributed as follows:
     9.1:   6, 10 = 1 point each; 12, 20 = 3 points each; 28 = 2 points;
     9.2:   9 = 3 points;
     9.3:   1, 9 = 3 points each; 17 = 2 points; 19, 20 = 3 points each;
     9.4:   1 = 2 points (no graph necessary); 7, 9 = 1 point each; 13 = 3 points.

Due Friday, April 14:
     7.2   19, 20, 28, 31;
     7.3   3, 7, 8, 17, 20, 31;
     7.4   2, 3, 9, 10, 15, 16, 29, 36;
     7.5   11, 31;
   solutions13.pdf
   Grading: 23 points, distributed as follows:
     7.2:   20, 28 = 2 points each;
     7.3:   3, 8 = 1 point each; 17, 20 = 2 points each, 31 = 3 points.
     7.4:   2, 10, 36 = 2 points each;
     7.5:   11 = 1 point, 31 = 3 points.
Due Friday, April 7:
     7.1   3, 7, 8, 13, 20, 21, 23, 28.
     7.2   3, 4, 5, 6, 14.
   solutions12.pdf
   Grading: 19 points, distributed as follows:
     7.1:   3 = 1 point, 8 = 2 points, 13 = 1 point, 20 = 2 points, 23 = 1 point, 28 = 2 points.
     7.2:   4 = 2 points, 6, 14 = 4 points each.

Due Friday, March 31: We restricted the problems on which you need to create "pplane" pictures: In 6.2 #19,27 use pplane to find and classify the other equilibrium solutions besides the origin, and print out a phase portrait for each problem. In 6.3 #8,10 create a phase portrait for the nonlinear system (3) and explain how your linearization compuations are reflected in the nonlinear behavior near the corresponding equilibria.
     6.1   5, 8, 11, 15, 20, 24
     6.2   5, 6, 7, 8, 9, 14, 15, 19, 27, 30
     6.3   8, 9, 10, 14, 15, 16, 17
     6.4   12, 13, 14, 15, 16.
   solutions11.pdf
   Grading: 35 points, distributed as follows:
     6.1:   5, 8, 11 = 1 point each; 15, 20 = 2 points each; 24 =1 point.
     6.2:   6, 8, 9 = 1 point each; 19 = 2 points, 27 = 3 points (pplane analysis is part of 19, 27); 30 = 3 points.
     6.3:   8, 10 = 2 points each, then 2 points for pplane picture and pointing out consistency between 8,10 and nonlinear problem; 16, 17 = 2 points each.
     6.4:   12, 14 = 3 points each (2 points for linearization, 1 point for understanding nonlinear equilibria in these difficult borderline cases).

Due Friday, March 24: except where indicated, work problems by hand, but feel encouraged to use technology to check.
     5.4   1, 7, 11, 29
     5.5   1, 3, 11, 23, 33, 36
     5.6   1, 13, 15, 19, 23 On 19 and 23 you may use technology to compute variation of parameters formulas for the solutions. For more specific problem by problem instructions, see mar20.pdf   lecture notes
   solutions10.pdf
   Grading: 34 points, distributed as follows:
     5.4:   1, 11, 29 = 3 points each;
     5.5:   1 = 2 points, 3 = 3 points, 11 = 2 points, 33 = 4 points, 36 = 2 points.
     5.6:   13, 15a, 19, 23 = 3 points each;

Due Friday, March 10: (accepted until March 17) Because of the Maple project, the entire assignment for this week may be done in groups of up to three people...hand in one assignment per group.
     5.2   2, 3, 9, 15, 27, 35 (You may use technology for eigenvectors, as long as you're sure you could find them by hand.)
     5.3   3, 7, 9, 14, 16, 17, 21 (interesting!)
     5.3   Maple exploration. See the paragraph near the bottom of page 327 which begins, "For your..." Here is a document we will discuss on Monday which contains useful commands, as well as another document which is a template you should use to carry out the project details:
       mar6maple.pdf   quaketemplate.pdf
       mar6maple.mws   quaketemplate.mws
   solutions9.pdf
   quakesols.pdf
   Grading: 39 points, distributed as follows:
     5.2:   3, 15, 27 = 3 points each.
     5.3:   3 = 2 points, 9 = 4 points, 14, 16 = 2 points each, 17 = 4 points.
     project:   2 = 2 points, 3, 4, 5, 6 = 3 points each; 7 = 2 points.

Due Friday, March 3:
     4.1   1, 8, 11, 15, 16, 21a, 24, 26.
     4.3   9   You may do (just) this problem in groups of up to three people. You will need to write some Runge Kutta code for first order systems!
     5.1   11, 13, 18, 21, 22, 26, 31, 35.
   solutions8.pdf
   Grading: 27 points, distributed as follows:
     4.1:   8, 16 = 2 points each; 21a = 1 point; 24, 26 = 2 points each.
     4.3:   9 = 8 points
     5.1:   13, 18 = 1 point each; 22, 26, 31, 35 = 2 points each.

Due Friday, February 24:
     3.6   4, 5, 7, 13, 16, 21, 22.
   solutions7.pdf
   Grading: 16 points, distributed as follows:
     3.6:   4, 5 = 3 points each, 13 = 4 points, 21, 22 = 3 points each.

Due Friday, February 17:
     3.5   3, 4, 17, 19, 36, 37, 43, 49, 50, 51, 64.
   solutions6.pdf
   Grading: 20 points, distributed as follows:
     3.5:   3 = 2 points, 17, 19 = 3 points each; 37 = 4 points, 43a, 43b, 49, 64 = 2 points each.

Due Friday, February 10:
     3.1   1, 2, 4, 5, 11, 13, 17, 27, 29, 30, 31, 33, 34, 35.
     3.2   2, 5, 9, 11, 13, 21, 22, 25, 26.
     3.3   3, 10, 14, 21, 22, 29, 33, 37.
     3.4   4, 5, 6, 13, 15, 19, 23.
   solutions5.pdf
   Grading: 35 points, distributed as follows:
     3.1:   2, 4, 11 = 2 points each; 17, 34, 45 = 1 point each.
     3.2:   2, 9, 13, 22, 26 = 2 points each.
     3.3:   10, 14 = 2 points each; 22 = 3 points, 29 = 2 points, 37 = 2 points.
     3.4:   4 = 3 points, 5, 6, 15 = 2 points each; 19 = 3 points, 23a = 1 point, 23b = 2 points.

Due Friday, February 3:   work in the same group as for the Maple project below, and hand in only one assignment per group...recall, groups are optional and consist of from 1-3 people.
     2.3   2, 3, 9, 11, 13, 14, 15, 16,17,18.
   solutions4.pdf
   Grading: 12 points, distributed as follows:
     2.3:   2a = 2 points, 2b = 1 point, 9, 11, 13 = 2 points each; 17 = 3 points.

Maple Project 1 due Friday February 3
     proj1probs.pdf    problems for Maple project 1, due Friday February 3
     proj1probs.mws    Maple worksheet
     numerical1.pdf    handout for numerical methods, sections 2.4-2.6
     numerical1.mws    maple worksheet
     2270tut.pdf    a brief intro to Maple in the Math Labs which we used in 2270.
     2270tut.mws
   proj1popans.pdf   populations; Investigation C solutions
   proj1numans.pdf   numerical work solutions
   Grading: 32 points, distributed as follows:
     1 = 8 points (a,b values = 2 points, line picture = 2 points, solution function P(t) and graph with points = 2 points, year 2025 est = 2 points); 2, 3 = 4 points each; 4a,b,c = 2 points each; 5, 6 = 6 points each; 7 = 4 points.

Due Friday, January 27:
     2.1   1, 4, 5, 10, 13, 15, 24
     2.2   5, 7, 9, 12, 21, 23, 24
   solutions3.pdf
   maplesols3.pdf   maple used to solve DE's and draw slope fields for hw
   maplesols3.mws
   Grading: 26 points, distributed as follows:
     2.1:   4, 5 = 3 points each (2 points solution formula, one point slope field picture); 10 = 2 points, 13ab = 1 point each; 15, 24 = 2 points each.
     2.2:   7, 9 = 4 points each (equilibria= 1 point, stability = 1 point, slope field and phase diagram = 1 point, solution formula = 1 point); 21ab = 1 point each; 24 = 2 points.

Due Friday, January 20:
     1.3   3, 6, 10, 11, 12, 13, 18, 21, 23, 29.
       in 6, also verify (show work) that y(x)=x+C*exp(-x) is the general solution, and compare (for yourself) this formula to the solution curves you sketched. In 18, explain why the existence and uniqueness theorem does not apply for this initial value problem, but then solve this separable equation to show that in fact there exist (at least) two solutions to the given initial value problem.
     1.4   9, 12, 19, 22, 35, 41, 43, 46, 54, 60, 66.
     1.5   1, 7, 13, 34, 36, 38, 41.
      Note that 1.3 #23, 1.4 #46, 60 are now optional.
   solutions2.pdf
   Grading: 33 points, distributed as follows:
     1.3:   6 (verify solution part) = 1 point, 12, 13 = 1 point each, 18 = 3 points (1 point for showing theorem does not apply, 2 points for finding two solutions to IVP), 21 = 2 points.
     1.4:   9, 12, 22 = 2 points each; 43, 54 = 2 points each; 66a = 1 point, 66b = 2 points.
     1.5:   7, 13, 34 = 2 points each; 38abc = 2 points each; 41 = 2 points.

Due Friday, January 13:
     1.1   3, 6, 15, 16, 19, 27, 31, 34, 35, 36;
     1.2   6, 7, 13, 18, 19, 21, 25, 29, 33, 34, 39.
   solutions1.pdf
   Grading: 21 points, distributed as follows:
     1.1:   6, 16, 19, 31 = 2 points each; 35, 36 = 1 point each.
     1.2:   6, 13, 18, 29 = 2 points each; 34 = 2 points, 39 = 1 point.