2019 Spring - MAT 2680 - Reitz

"...how it differs from the rocks"

Category: Assignments (Page 2 of 3)

OpenLab #2: Numerical methods PROJECT – Example Data

March 14, 2019 / / 0 Comments

Below you will find complete solutions for the Example given the previous post – you can use this to test your project.

Example.  Given the differential equation dy/dx=x^2-0.5xy and initial condition y(1.5)=2.2, approximate the value of y(2.5) using step size h=0.05

ACTUAL ANSWER: y(2.5) = 3.49201…

Euler’s Method
i h x_i y_i k = f(x_i,y_i) y_(i+1)
0 0.05 1.5 2.2 0.6 2.23
1 0.05 1.55 2.23 0.67425 2.2637125
2 0.05 1.6 2.2637125 0.74903 2.301164
3 0.05 1.65 2.301164 0.8240397 2.342365985
4 0.05 1.7 2.342365985 0.8989889128 2.387315431
5 0.05 1.75 2.387315431 0.9735989982 2.435995381
6 0.05 1.8 2.435995381 1.047604158 2.488375588
7 0.05 1.85 2.488375588 1.120752581 2.544413217
8 0.05 1.9 2.544413217 1.192807443 2.60405359
9 0.05 1.95 2.60405359 1.26354775 2.667230977
10 0.05 2 2.667230977 1.332769023 2.733869428
11 0.05 2.05 2.733869428 1.400283836 2.80388362
12 0.05 2.1 2.80388362 1.465922199 2.87717973
13 0.05 2.15 2.87717973 1.52953179 2.95365632
14 0.05 2.2 2.95365632 1.590978049 3.033205222
15 0.05 2.25 3.033205222 1.650144125 3.115712428
16 0.05 2.3 3.115712428 1.706930708 3.201058964
17 0.05 2.35 3.201058964 1.761255718 3.289121749
18 0.05 2.4 3.289121749 1.813053901 3.379774445
19 0.05 2.45 3.379774445 1.862276305 3.47288826
20 0.05 2.5 y(2.5) = 3.47288826

 

 

 

 

 

Improved Euler’s Method
i h x_i y_i k1 z_(i+1) k2 y_(i+1)
0 0.05 1.5 2.2 0.6 2.23 0.67425 2.23185625
1 0.05 1.55 2.23185625 0.6728114063 2.26549682 0.7476025438 2.267366599
2 0.05 1.6 2.267366599 0.746106721 2.304671935 0.8211456538 2.306547908
3 0.05 1.65 2.306547908 0.8195979758 2.347527807 0.8946013641 2.349402892
4 0.05 1.7 2.349402892 0.8930075421 2.394053269 0.9677033899 2.395920665
5 0.05 1.75 2.395920665 0.9660694182 2.444224136 1.040198278 2.446077357
6 0.05 1.8 2.446077357 1.038530378 2.498003876 1.111846414 2.499836777
7 0.05 1.85 2.499836777 1.110150981 2.555344326 1.18242289 2.557151124
8 0.05 1.9 2.557151124 1.180706432 2.616186446 1.251718216 2.61796174
9 0.05 1.95 2.61796174 1.249987303 2.680461105 1.319538895 2.682199895
10 0.05 2 2.682199895 1.317800105 2.7480899 1.385707852 2.749787594
11 0.05 2.05 2.749787594 1.383967716 2.81898598 1.450064721 2.820638405
12 0.05 2.1 2.820638405 1.448329675 2.893054889 1.512465995 2.894658297
13 0.05 2.15 2.894658297 1.510742331 2.970195413 1.572785045 2.971746481
14 0.05 2.2 2.971746481 1.571078871 3.050300425 1.630912022 3.051796253
15 0.05 2.25 3.051796253 1.629229215 3.133257714 1.686753629 3.134695825
16 0.05 2.3 3.134695825 1.685099802 3.218950815 1.740232793 3.220329139
17 0.05 2.35 3.220329139 1.738613261 3.307259802 1.791288237 3.308576677
18 0.05 2.4 3.308576677 1.789707988 3.398062076 1.839873957 3.399316225
19 0.05 2.45 3.399316225 1.838337624 3.491233107 1.885958617 3.492423631
20 0.05 2.5 y(2) = 3.492423631

 

 

 

 

Runge-Kutta
i h x_i y_i k1 = f(x_i,y_i) k2 = f(x_i+.5h,y_i+.5hk1) k3 = f(x_i+.5h, y_i+.5hk2) k4 = f(x+h,y+hk3) Runge-Kutta y_(i+1) = y_i + h*(k1+2k2+2k3+k4)/6
0 0.05 1.5 2.2 0.6 0.6366875 0.6359881445 0.6728554594 2.23181839
1 0.05 1.55 2.23181839 0.6728407481 0.709821466 0.7090934081 0.746181552 2.267292157
2 0.05 1.6 2.267292157 0.7461662747 0.7832936203 0.7825394711 0.8197042176 2.306438296
3 0.05 1.65 2.306438296 0.8196884061 0.8568207014 0.856043244 0.8931456109 2.349259645
4 0.05 1.7 2.349259645 0.8931293019 0.9301304558 0.9293326184 0.9662395087 2.395745436
5 0.05 1.75 2.395745436 0.9662227434 1.002962858 1.002147687 1.038732462 2.445871905
6 0.05 1.8 2.445871905 1.038715285 1.075071194 1.074241825 1.110384803 2.499602956
7 0.05 1.85 2.499602956 1.110367265 1.146222996 1.145382627 1.180971517 2.556890873
8 0.05 1.9 2.556890873 1.18095367 1.216200837 1.215352702 1.250282954 2.617677071
9 0.05 1.95 2.617677071 1.250264856 1.284802979 1.283950319 1.318125413 2.681892878
10 0.05 2 2.681892878 1.318107122 1.351843875 1.350989913 1.384321567 2.749460347
11 0.05 2.05 2.749460347 1.384303145 1.417154527 1.416302445 1.448710757 2.820293079
12 0.05 2.1 2.820293079 1.448692267 1.480582715 1.479735625 1.51114915 2.894297063
13 0.05 2.15 2.894297063 1.511130657 1.541993079 1.541154007 1.57150976 2.971371518
14 0.05 2.2 2.971371518 1.57149133 1.601267084 1.600438946 1.629682352 3.051409732
15 0.05 2.25 3.051409732 1.629664051 1.658302858 1.657488442 1.685573222 3.134299898
16 0.05 2.3 3.134299898 1.685555117 1.713014923 1.712216872 1.739104879 3.219925928
17 0.05 2.35 3.219925928 1.739087035 1.765333814 1.764554613 1.79021561 3.308168257
18 0.05 2.4 3.308168257 1.790198091 1.815205609 1.814447568 1.838858971 3.398904619
19 0.05 2.45 3.398904619 1.838841842 1.862591365 1.861856614 1.885003188 3.492010794
20 0.05 2.5 y(2.5) = 3.492010794

OpenLab #2: Numerical methods PROJECT – Part 1

March 12, 2019 / / 2 Comments

Numerical methods provide a way to compute (approximate) values of solutions to differential equations, even when we cannot solve the equations exactly.  The drawback is the large number of numerical calculations required to obtain a desired value and level of precision.  In this project, you will use technology to implement the various numerical methods and use your technological solution to solve differential equations problems.

Assignment (Due Tuesday, April 4th).  Create a numerical methods calculator.  You can choose your technology tool for this job – use any one of the following:

  1. a spreadsheet (Excel, Google Sheets, or other spreadsheet)
    • if you choose to create a spreadsheet, you should have columns forx, y, f(x,y) , and so on, and each stage should appear in its own row
  2. a programming language (Java, Perl, or other programming language)
    • if you choose to write code, your program should output the values of x, y, f(x,y) and so on at each stage
  3. mathematical software (MatLab, Maple, Mathematica, or other mathematical software)
    • if you choose to use mathematical software, your program should output the values of x, y, f(x,y) and so on at each stage

How to submit. Part 2 of this project will talk about how to submit your project – you will be asked to upload your solution (spreadsheet, or code, or mathematical software document) and to write  about what you did.  For now, focus on getting your solution working.

Requirements:

  1. Your solution should allow you to solve problems of this type:

Example.  Given the differential equation dy/dx=x^2-0.5xy and initial condition y(1.5)=2.2, approximate the value of y(2.5) using step size h=0.05

  1. Your solution must be able to carry out Euler’s Method, Improved Euler’s Method, and Runge-Kutta (you may implement these as three separate spreadsheets or programs if you wish).
  2. Your solution should display all the points (x,y) found along the way, not just the final point.
  3. Your solution should also display other values found while carrying out each method:
    1. Euler’s Method: display the slope f(x,y) at each stage
    2. Improved Euler’s: display the values of k1, k2 at each stage
    3. Runge-Kutta: display the values of k1, k2, k3, k4 at each stage
    4. You can display other values as well, if you wish (for example, the intermediate y-value in the Improved Euler method that we refer to as z).
  4. Your solution may NOT use any built-in version of these methods (for example, most mathematical software contains a built-in command for Euler’s Method – you can use this to check your work, but you need to create your own solution).
  5. You should be able to relatively easily change the initial condition, step size, and target value.
  6. You should be able to relatively easily change the differential equation (it is ok if the equation is hard-coded into your program).

Test your project.  Solution data for the above example using Euler, Improved Euler, and Runge-Kutta will be posted this weekend so you can test your project.  You can also use examples from class to test your work, since you know what the solutions are.

 

Exam 1 Grades are posted, and SPECIAL OFFER

March 4, 2019 / / 0 Comments

Hi everyone,

The grades for Exam 1 are posted (under Dashboard/OpenLab GradeBook).

With some exceptions, you will notice that the scores are not as high as you might have liked!  This exam covered a lot of material, and relied on a great deal of prior knowledge and skills (especially Calculus and Algebra).  With that in mind, I am giving you the option to improve your score through the ONE-TIME SPECIAL OFFER below (note: this offer will almost certainly *not* be repeated on future exams), due in two weeks on Tuesday 3/19.

Let me know if you have any questions,
Prof. Reitz

Exam 1 Special Offer – earn bonus points.  You can improve your grade on the exam, by doing the following:

  1. Choose ONE OR TWO problems in which you did NOT earn full points.  You are working to earn back (some of ) the points you missed on this problem.  For each problem you chose:
  2. Do the problem over, neatly and completely, start to finish, on a separate sheet of paper.
  3. Include the following information on the sheet:
    1. Your name
    2. The date
    3. The problem number
    4. Your original score on the problem (out of 25)
  4. On the same sheet, write a short paragraph (at least two complete sentences) explaining why you lost points.
    1. If you lost points due to a mistake or mistakes, explain what you did wrong (this is to let me know that you understand your error).
    2. If you lost points due to not completing the problem, then explain how to solve it (this is to let me know that you have learned how to solve it).
  5. Hand in your original exam and your corrected problem(s) and explanation(s), stapled together, in class on Tuesday, 3/19.
  6. Bonus points will be added to your Exam score based on the number of points you missed on the chosen problem(s),  the accuracy of your corrections and explanation, and your overall grade on the exam.  Bonus points are limited as follows:
    1. If you received less than 50% on the exam, you can earn a maximum of 30 bonus points.
    2. If you received between 50% – 59% on the exam, you can earn a maximum of 20 bonus points.
    3. If you received between 60% – 69% on the exam, you can earn a maximum of 15 bonus points.
    4. If you received between 70% – 79% on the exam, you can earn a maximum of 10 bonus points.
    5. If you received between 80% – 89% on the exam, you can earn a maximum of 5 bonus points.
    6. If you received 90% or more on the exam, you may not earn any bonus points.

 

Assignments Week 4

February 19, 2019 / / 0 Comments

Exam #1 will take place on Tuesday, 2/26, covering material through Sec 4.1.  A review sheet will be distributed on Tuesday, 2/19, and posted to the OpenLab.

WeBWorK: Assignment  6a-Modeling-Population will be due on Tuesday, 2/26, at midnight.
NOTE: Assignment 6b-Modeling-Cooling will be due one week after the exam, on Tuesday, 3/5, at midnight.

OpenLab:  none

Assignments Week 3

February 14, 2019 / / 0 Comments

WeBWorK:  Assignment 5-Exact Due Tuesday 2/19 at midnight
NOTE: As announced in class today, the WeBWorK assignments from last week have been extended until next Tuesday, 2/19 at midnight:
 3-Separable ,  4-Bernoulli-nosub and  4b-Homogeneous-YoverX due Tuesday 2/19 at midnight.

OpenLab:  none

Assignments Week 2

February 5, 2019 / / 0 Comments

NOTE: City Tech will be closed next Tuesday, 2/12/19, for President’s Day. 

WeBWorK:  3-Separable ,  4-Bernoulli-nosub and  4b-Homogeneous-YoverX. Due Thursday 2/14 at midnight
OpenLab:  Complete your first OpenLab Assignment “Advice from the Past” by Thursday, 2/14, at the beginning of class.

OpenLab #1: Advice from the Past

February 5, 2019 / / 50 Comments

In Fall 2014 I taught this course and at the end of the semester, I gave my students the following assignment:

Imagine that you are invited to speak on the first day of MAT 2680, to give advice to entering students.  Write at least three sentences … describing what you would tell them.

To see the assignment and the students’ responses, follow this link.

Your assignment, due at the beginning of class next Thursday, February 14th, is to:

  1. Read through ALL the responses (there are 63 of them, but many of these are short replies to other comments).
  2. Write a reply to this post (1 paragraph) responding to all of the following:
    1. What advice seemed most relevant to you personally? Why? (you can copy/paste a short statement, or put it in your own words)
    2. Based on this advice, what changes can you make right now to help you succeed in this course?

Extra Credit. For extra credit, write a response to one of your classmates’ comments.  Do you have any advice?  Be kind.

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