# 21-260: Differential Equations

### Description

The subject of differential equations can be described as the study of equations involving derivatives. It can also be described as the study of anything that changes. The reason for this goes back to differential calculus, where one learns that the derivative of a function describes the rate of change of the function. Thus any quantity that varies can be described by an equation involving its derivative, whether the quantity is a position, velocity, temperature, population or volume.

There are three main ways to study differential equations. There are analytic methods, wherein a mathematical formula for a solution of a differential equation is obtained. There are Numerical techniques, which provide an approximate solution, generally using a computer or programmable calculator. Differential Equations can also be studied qualitatively, determining general properties of solution without concern for exact behavior.

In this course, we will emphasize analytic methods, though qualitative and numerical techniques will make brief appearances.

### News

Wednesday 10 May: Solutions to Exam #3 are available in the hall outside WEH 6213.

Monday 8 May: Dr. Handron's Office Hours this week will be Wednesday, 10:00-12:00 and Thursday 10:00-12:00, 2:00-3:00. The final exam will be given on Friday. See the exam review page for details.
Friday 5 May: The Final Exam review has been posted. Follow the link from the Schedule Page.

Saturday 29 April: The reading and homework assignments for Weeks #13 and #15 have been posted. Follow the links from the Schedule page.
Wednesday 19 April: The reading and homework assignments for Weeks #13 and #14 have been posted. Follow the links from the Schedule page.
Wednesday 19 April: I've updated the statistics page to include Exam #3.
Thursday 13 April: Well, I wrote up a nice Exam #3 for you, and when I was done, there was no material from Section 9.3 covered. I thought you'd all like to know that.
Wednesday 12 April: You can ignore problem #5 on the "old exam problems" for Exam #3. It covers material from Section 6.3, which is not covered on this exam. Additionally, note that the exam will be give during class time in UC McConomy, and the review session will be given Thursday from 7:00-8:30 in DH 2315.
Tuesday 11 April: The link (from the Exam #3 review page) to the old exam problems has been corrected. It should work now.
Friday 7 April: The reading assignment for Week #12 has been posted, as has a review page for Exam #3. Follow the links from the Schedule page.
Tuesday 4 April: The Final Exam has been scheduled for Friday 12 May, from 8:30-11:30am. Please take this into account when making your travel plans.
Monday 3 April: HW#11 is really due on Friday 7 April.
Friday 31 March: The reading and homework assignments for Week #11 have been posted. Follow the links from the Schedule page.
Wednesday 29 March: I've updated the statistics page to include Exam #2.
Monday 27 March: Now the reading and homework assignments for Week #10 are linked to as well as posted.
Saturday 25 March: The reading and homework assignments for Week #10 have been posted. Follow the links from the Schedule page.
Tuesday 21 March: Due to the closing of the OSC, Jeff Eisenbeis will hold his office hours in PPB 342 from now on.
Monday 20 March: The review session for Exam #2 will be held tonight, from 6:30-8:00 in DH 2315.
Wednesday 8 March: Dr. Handron will not be holding his regularly scheduled office hours on Thursday 9 March. You should make use of your recitations and TA's office hourse instead.
Wednesday 8 March: The reading assignment for Week #9 has been posted, as has a review page for Exam #2. Follow the links from the Schedule page.
Friday 3 March: The reading and homework assignments for Week #8 have been posted. Follow the links from the Schedule page.
Wednesday 1 March: Here are some supplementary notes on The Wronskian and fundamental sets of solutions.
Tuesday 28 February: HW#7 is due on 3 March, not 14 October. I've corrected the assignment page.
Tuesday 28 February: I've made some corrections to the statistics page posted last week. These changes affect the calculation of the "Mean by Recitation" column. You may wish to look at the corrected entries.
Thursday 9 February: The reading and homework assignments for Week #7 have been posted. Follow the links from the Schedule page.
Wednesday 22 February: Here are some statistics for the course, including information about Exam #1.
Sunday 19 February: The homework assignments for Week #6 is due on Friday 24 February, not 7 October.
Friday 17 February: The reading and homework assignments for Week #5 Week #6 have been posted. Follow the link from the Schedule page.
Tuesday 14 February: Happy Valentine's Day. I'll extend tonight's review session an extra half hour, to 9:00, since I understand some of you have committments earlier in the evening.
Monday 13 February: I've updated the Exam #1 Review Page. I'll hold a review session tomorrow (Tuesday) evening from 7:00-8:30 in PH 100.
Friday 10 February: Here are some notes that cover the matrix algebra topics we will be needing. They may make a helpful additional reference for you.
Thursday 9 February: The reading assignment for Week #5 has been posted, as has a review page for Exam #1. Follow the links from the Schedule page.
Thursday 9 February: Sorry I wasn't able to be with you yesterday. I'm feeling much better today. Because we didn't get to cover everything I intended, I'll have to make a change to tomorrow's homework. I think the most straightforward thing to do is to simply remove the problems in section 7.2 from the assignment. I've indicated that on the assignment page. Sorry about the late change. I'll see you tomorrow.
Friday 3 February: The reading and homework assignments for Week #4 have been posted. Follow the link from the Schedule page.
Monday 30 January: A black camera bag was left in WEH 7500 by a student after lecture today. (This would be the 12:30-1:20 lecture.) If any of you found it or know where it might be, please let me know and I'll pass the information along.
Monday 30 January: The date of Exam #3 has been changed. The new date is Friday 14 April. This is the Friday before the originally scheduled date.
Thursday 26 January: The reading and homework assignments for Week #3 have been posted. Follow the link from the Schedule page.
Friday 20 January: The reading and homework assignments for Week #2 have been posted. Follow the link from the Schedule page.
Thursday 19 January: I (Dr. Handron) will be holding office hours today in my office (WEH 6214) from 1:30-3:30pm. My normal office hours for the semester will be 1:30- 3:30 3:20pm on Wednesdays and Thursdays, or by appointment.
Wednesday 18 January: Please see this week's assinment page for instructions for turning in your homework.
Wednesday 18 January: I've added some (hopefully) helpful information about kinetic and potential energy to the HW#1 assignment page. This should help with problem 1.3.30.
Tuesday 17 January: I've corrected the due date for the first homework assignment. It will be due this Friday, 20 January, not on 2 September, as originally posted.
Also, the midterm Exam #3 will be given on Wednesday 19 April, rather than 19 May as listed on the syllabus handed out in class.
Finally, the TA for Section H will be Christopher Mirabito, not Mirabato, as on the front of the syllabus handed out in class.
Monday 16 January: Starting next week, we will be using the Java applets dfield and pplane for some of our work. You may want to take a look and try them out beforehand. Dfield will make more sense after reading the examples in Section 1.1 of the text. The name dfield is short for "direction field."
Monday 16 January: Welcome to 21-260 Differential Equations.