Math 234 — Homework


Syllabus  |  Homework assignments  |  About the exams  |  Using your computer  |  Lecture schedule
Each week you will find a homework assignment here. It will always consist of a reading assignment and a list of problems to do. You should be doing these problems on your own, or, better with a group of friends. In discussion your TA can help you with the problems that cause the most headaches. You can use the piazza site for questions: keep checking—maybe someone asked a question you’re stuck with, or one you know how to answer, or maybe someone asked something you didn’t know you didn’t know.

The bi–weekly quizzes will be based on the homework and reading assignments.


Homework and reading entries so far on this page:

September 2, 4
On Wednesday we covered the material in sections 1—6, Chapter 1 of the text. We will cover the second half of Chapter 1 on Friday.
Reading: Chapter 1.
Problems: 1—15 from Chapter 1, and problems 1 and 2 from Chapter 2.

In questions that were asked on piazza, the following two clippings from the math 222 text appeared.


September 9, 11
We reviewed the cross product and started on vector functions (chapter 2). After having seen linear and circular motion we started on the cycloid example, and also the helix. We started discussion of the derivatives of vector functions.

Reading: Chapter 2.

Problems: All problems from Chapter 2. Until Monday’s lecture, when I will explain tangent, unit tangent, acceleration vector and arc length, these problems will be hard to do. So instead of trying to do the problems, read the problems, then read the text: read chapter 2! Which sections have been covered in lecture already? Which sections look like they might be useful in the problems?

Extra problems on lines: Here are some problems on parametric representation of lines with answers.

About problem 4. Here is a short animation of the curves and lines that appear in Problem 4 of Chapter 2. The animation shows


And here is an animation of how the cycloid comes about:


September 14, 16, 18
We finished chapter 2 on curves and vector functions and started chapter 3 on functions of several variables. On Monday and Wednesday next week, we will see quadratic functions of two variables and how to classify them as positive, negative, or indefinite, using good old “completing the square.”

Reading: Chapter 3, section 1, 2, and 3.

Problems: Chapter 3 (p.46) 1—7, 9, 10.


September 21, 23, 25
We finished Chapter 3 and started on chapter 4 (partial derivatives).

Reading: Chapter 3 and Chapter 4, §1–2.

Problems: Prepare for the midterm next week, see the exam page


September 28, 30, October 2
The midterm was on Wednesday. On Monday and Friday we saw the linear approximation formula, the equation for the tangent plane, and the chain rule that tells us how to differentiate $\frac{df(x(t), y(t))}{dt}$.

Reading: Chapter 4: §2 has a detailed explanation of the linear approximation formula. §4 explains what the error term is—read it to see what we are ignoring most of the time. §5 is about tangent planes and §6 presents the chain rule.

Problems: Chapter 3 (p.48) 14 (pick a few; the desmos grapher has answers), 16, 17.

Chapter 4, §3, problems 1, 2 (pick a few, do more later). See using your computer for a demo on how to use the Google grapher to make 3D graphs.

Chapter 4, §3 problem 6. §7, problems 1, 2, 3, 6a, 8.


October 5, 7, 9
This week we met the gradient of a function, which lets you write the chain rule in vector form.

Reading: Sections 8, 9, and 10 from chapter 4.

Problems: Right after §10, starting on page 72:


October 12, 14, 16
Chain rule for functions of several variables, especially, how to compute the derivatives of expressions like $f(x(u, v), y(u,v))$.

We saw Clairaut’s theorem which says that mixed partials don’t depend on the order of the derivatives: $f_{xy}=f_{yx}$. Related: when can you, and how do you find a function $f(x,y)$ if you are given its derivatives $f_x$ and $f_y$?

Friday’s lecture showed you a derivation of the “wave equation” which describes a vibrating string (and many, many more things). Here are the slides and here are the graphs on the desmos website.

Reading: Section 11 from chapter 4, in particular examples 11.1 and 11.3.

Problems:


October 19, 21, 23
We started Chapter 5 on Optimization. Definitions of local/global maximum and minimum, interior and boundary point of a region; def of “closed region”. Main theorems in §2.1 and §4.2. The “fishy example.” On Friday we ended by looking at linear regression.

Reading: Chapter 5, §1—7.

Problems: from Chapter 5.


October 26, 28, 30
On Monday we saw Taylor’s formula for two variables, on Friday we applied this to the second derivative test. The example we saw was the function $f(x,y) = x^3+y^3-3xy$ (we didn’t discuss the zero set, but it is a “famous curve” called the Folium of Descartes. See also wikipedia)

Reading: Chapter 5, §9 covers the Taylor expansion and the 2nd derivative test. In the coming week we will be seeing the method of Lagrange multipliers, which is presented in §12.

Problems: all from Chapter 5, § 10:

This section has many more problems. Keep those for midterm practice.


November 2, 4, 6
We saw Lagrange’s method for finding maxima and minima when their are constraints. On Wednesday we went through an example from economics involving the Cobb—Douglas production function. On Friday we started on double integrals.

Reading: For Lagrange multipliers make sure you understand Figure 8 on page 102. For double integrals read §1 and §2 of Chapter 6. In particular look at figures 3 and 4 on page 111 and compare with figure 1 on page 107.

Problems:


November 9, 11, 13
Double integrals, iterated integrals, integrals in polar coordinates. We finished with a computation of the area under the “Bell curve” (you can find the whole story on Wikipedia; see “computation by polar coordinates” on this page for the derivation I gave).

Reading: Finish Chapter 6 on integrals. In particular,

Problems:


November 16, 18, 20
We saw how to set up a triple integral that computes the kinetic energy of a rotating body and examples of how to compute such triple integrals in cylindrical coordinates and spherical coordinates.

Reading: Review previous reading about double integrals, triple integrals, and cylindrical and spherical coordinates. Then begin the last chapter, Chapter 7 on Vector fields and line integrals. In particular, §1—2 which give examples of vector fields.

Problems:


November 30, December 2, 4
We started on vector calculus, the last topic in this course.

Reading: Chapter 7, sections 1—11.

Problems: