Problem Contest

Last Friday, I started class with an announcement of a problem solving contest. If you are interested in participating, you can go to the Spring Problem Solving Contest website for more information.

Office Hours for Tuesday 2/27

I haven't been very good about posting to the blog lately, but I'll try to keep up with it more. How's this: I'm going to have to move my office hours on Tuesday to later in the day. Rather than 10:30am-12:20pm, I'll plan to hold them from 4:00pm to 6:00pm.

Assignment for Week #7

I posted the assignment for Week #7 on Friday afternoon, but I didn't get a chance to post about it here until now. You can find it by following the link from the Schedule page. There are a couple "home-made" additional problems that I will add on Monday afternoon.

UPDATE: I've added the additional problems to the homework page for Week #7. Try refreshing your browser if they don't show up.

UPDATE: In problem 7.4.2, you should skip part (d). Do only parts (a), (b) and (c).

Assignment for Week #6

There will be a homework assignment for Week #6, but it's likely I won't get to post it until Monday, or maybe Sunday evening. If you are anxious to get started, you can be sure that the problems 7.3.6 and 7.3.10 will be on it. You can get to work on those.

UPDATE: The assignment has been posted. It does, indeed, include 7.3.6 and 7.3.10. You can follow the link from the Schedule Page to find out the other problems.

Sections A and B

In case any of you cannot make it to the office hours today, you can collect your homework and solutions from outside my office. Homeworks 1 to 4 of each section are in a box and you can also find solutions to all the assignments. My office is WeH 7215.

mistakes hw 4

In the set of solutions that I wrote to hw 4 there are two mistakes, but I don't want to waste paper and print new copies of the solutions, so I'll just post here the corrections. 1 In exercise number 7.2.1 part d the element in the second raw and first column should be 14, not 7 as I wrote. 2 In the first additional exercise part b all the directions that I draw should be rotated counterclockwise by 90 degrees. So for example for R bigger then 4 and F bigger then 1.5 the answer would be Up Left instead of Up Right etc.

Exam #1 Review Session

I'll be holding a review session tonight, from 8:00-9:30pm. It will be held in DH 2315. This will be a good chance for you to ask questions about the review problems.

Office Hours before exam

Because of the exam next Wednesday I'll hold office hours on Monday from 5:00 to 6:00 instead of Wednesday. The Tuesday office hours are unchanged, from 3:30 to 5:00. For those of you who don't know where the Physical Plant Building is, here are the directions. If you can't make it to office hours, you can pick up all old homeworks and solutions in a box outside my office, after the Monday office hours.

changed office hours

Just for the next week I'll have office hours on Monday from 5 to 7 pm instead of Thursday from 10:30 to noon, so you can come to pick up your graded homeworks with the solutions. I'll have as usual office hours on Monday from 10:30 to noon as well, but I cannot give you the hws and the solutions at that time.

Turning in Late Homework

According to the policy set out on the Grading Page of the 21-260 Website, I accept late homework until the solutions are distributed. This typically happens during recitation six days after the due date.

Since Exam #1 will be held next Wednesday (You remembered Exam #1, right -- more on that later) graded homework and homework solutions will be distributed starting Monday afternoon. If you plan to turn in late homework, as some athletes do this week, you must turn it in to me by 1:20. You can give it to me during lecture, or put it in my mailbox.

How About a Cell Phone?

Someone left a cell phone in WEH 7500 after today's 12:30 lecture. If you are missing your phone, let me know. I'll hold onto it for a few days and if no one comes to claim it I'll sell it on ebay leave it with the information desk at the University Center.

Missing a Calculator?

I received this email from a student last week.

I am in Graph Theory in A51 after your class. A student left a calculator on (TI-83) one of the tables. If anybody asks, it has been turned into the UC info desk lost-and-found.

If you are missing a calculator, this may be yours.

Assignment for Week #4

The reading and homework for Week #4 have been posted. Follow the link from the Schedule Page of the course website.

UPDATE: You should feel free to use the program pplane wherever you are asked to sketch direction fields in a phase plane, or produce sketches of solution curves in the phase plane.

UPDATE: We did not get to cover linear independence of vectors this week, so I have removed problems 7.3.6 and 7.3.10 from the assignment. They will return on the next assignment, after next week's exam.

UPDATE: There is one other bit of information that will help with problem 7.2.22: If you have a matrix (or a vector) with entries that depend on t, then to differentiate that matrix (or vector) you simply differentiate each component separately.

For example the derivative, with respect to t, of [f(t) g(t)] is

[(df/dt) (dg/dt)].

I've asked your TA's to comment on this in tomorrows recitation.

Move Exam #3?

It has come to my attention that the Wednesday before Spring Carnival is an unpopular time to hold an exam.

It seems that it may be possible to move the exam to the preceeding Friday (Friday, April 13). Unfortunatly, there is nothing to be done about the whole 7:30 in the morning business. Unless I hear strong complaints about this change over the next few days, I will move the exam.

UPDATE: I will move Exam #3 to Friday, April 13.

The Blackboard Site is Available

I've made the Blackboard site available. It looks like all the grades for HW#1 have been recorded, as well as some grades for HW#2. For news and information about the course, you should check the course website, or this Blog. I'll try to keep them both updated. The Blackboard site will mainly be there for you to check your grades.

Assignment for Week #3

The reading and homework for Week #2 have been posted. Follow the link from the Schedule Page of the course website.

There are a couple "homemade" problems this week. They are available in a pdf file linked from the assignment page. You only need to complete the first two (this week). Early next week I'll post a new pdf file with only those problems you need to complete.

UPDATE: For problem 2.3.15 you will want to use dfield, or some other technology. You will find it quite difficult to complete the integration by hand. Additionally, problem 2.5.7(b) makes some comments about the phase line for the differential equation in question. You should actually show the phase line in your solution. Problem 2.5.20(b) is also simplified greatly by looking at the phase line, though it is not, strictly speaking, necessary.

Problem 2.3.8

I've been asked to comment on problem 2.3.8, in which you are asked to find the rate of return required for an investment of $2000 per year to grow to $1,000,000 over the course of 40 years. To complete this problem, as noted by commenter "anonymous" to this post, you must solve an equation of the form (e^(rt)-1)/r=[constant].

I didn't remark on this earlier, because I though commenter Jeffrey addresses the situation adequately. You will have to find some way to solve this numerically. If your calculator has a "solver" you can use that. Another method would be to graph the function f(r)=(e^(rt)-1)/r-[constant] and determine (by inspection) where it crosses the x-axis. Newton's method could, in principle, be employed, but it gets unwieldy rather quickly.

Sections A & B

Some of you have not collected your graded homework from last week and/or solutions of Homework 1 . Please stop by my office to collect these. I won't be carrying them to class next week.

Office Hours for Dr. Handron

This semester, starting tomorrow, I'll hold regular office hours on Tuesdays, from 10:30-12:20, and on Wednesdays, from 1:30-3:20. I'll be in my office during those times, and you can see me to discuss any aspect of the course (homework, previous grades, etc.)

Assignment for Week #2

The reading and homework for Week #2 have been posted. Follow the link from the Schedule Page of the course website.

A number of the problems will require you to use some sort of computer technology. I would recommend the Java applet dfield, which I will be demonstrating in class on Monday and/or Wednesday.

UPDATE: I've made a slight modification to the homework exercises for Week #2. I've removed 1.1.27 and 2.1.15 from the assignment, and added 1.2.16, 2.3.4 and 2.3.8.

UPDATE: I've also removed 2.2.22, and added 2.3.6.