Detailed schedule for Math 241.

Green is for "todo" items

Absences
Nathan: October 12-15
Jake:
Burak:
Xuan:

Nathan's notes for what was actually covered in lecture. I write the "Last time" parts up on the board before class starts and usually talk about them for 1 or 2 minutes (or even less). Also "This lecture is fine" means I covered everything with a minute or two left over.

Math 241: Week 1

Aug 24
Introduction (§12.1). Notes.
HW 1 (Due Fri Aug 28)

This lecture should take 40 minutes, leaving 10 minutes to discuss the syllabus, assuming you start on time. When covering distance in n-dimensions, it would be better to first compute the distance from the origin O to P and also to label the points as O and P in the 2D and 3D examples.
2025 and 2026: I got through the lecture in about 35 minutes.

Aug 25
Review of parts of Calc I and II. Worksheet. Solutions.

Final exam schedule request due.

Aug 26
Vectors (§12.2) and the dot product (§12.3). Notes.
HW 2 (Due Mon Aug 31)

Do not cover the derivation of the dot product on page 6. You want at least 15 minutes for the dot product, which requires skipping position vectors and some properties of the vector operations. Also, while we usually think of theta as the smaller of the two angles on page 5, the formula also works for the other one as the cosines are the same.
2025 and 2026: I had 20 minutes left for the dot product in both sections. In one case, I ended five minutes early.

Aug 27
Parametric curves via vector arithmetic. Worksheet. Solutions.
Aug 28
Dot product applications (§12.3) and equations for planes (§12.5). Notes.
HW 3 (due Wed, Sept 2)

This lecture is way too long as written. You should skip the discussion of regression and complete the discussion of projection and work in about 15 minutes. I usually start the plane examples/problems (bottom of page 4), with 20 minutes left. This is OK, but the answer A2 was packed into just a couple minutes.
In 2026, I ran out of time for A2 in the second hour.

Notes:
Pickup syllabus if you weren’t here on Monday.
Problems accessing Cengage/WebAssign? Get help from their Illinois specific help page.
Class website: http://dunfield.info/241.

Math 241: Week 2

Aug 31
Cross product (§12.4). Notes.
HW 4 (Due Fri, Sept 4)

Only cover through the triple product on page 5. Expect to have about 5 minutes each for the example at the bottom of page 4 and the triple product.
2025 and 2026: In one section, had only three minutes for the triple product.

Sept 1
Parametric curves via vector arithmetic. Worksheet. Solutions.
Sept 2
Functions of several variables (§14.1). Notes.
Hopf fibration video.
HW 5 (Due Tues, Sept 8 due to Labor Day.)

I find there's not time for both the plane example on page 6 and the Hopf fibration video. I do the video, and hit the 3-variable function at the top of page 7 with 10 minutes left.

Sept 3
Visualizing quadric surfaces. Worksheet. Solutions.
Please bring a laptop or tablet to section today.

Assign midterm exam rooms based on current enrollments (Nathan)

Sept 4
Level sets in 3d (§14.1); quadric surfaces (§12.6); intro to limits (§14.2). Notes.
Interactive guide to quadric surfaces.
More on limits.
HW 6 (Due Wed, Sept 9)

Using the Interactive Gallery to breeze through quadrics, I start in on limits at 20 minutes in. I then cover everything except the example on the middle of page 6.

Notes:
No class Monday, Sept 7 (Labor Day).
Class website: http://dunfield.info/241.
If you have a laptop or tablet, please bring it to section next week on Tuesday.

Week 3

Sept 7
Labor Day, no class and HW 5 is due tomorrow not today.
Sept 8
Visualizing quadric surfaces. Worksheet. Solutions.
Please bring a laptop or tablet to section today.
Sept 9
Limits in several variables (§14.2). Notes.
Extras: Limit pictures; The sinking of the Sleipner A.
HW 7 (Due Mon, Sept 14)

Cover up to the top of page 5, just before "rules for limits". This leaves time enough to do the limit pictures Mathematica notebook and tell the sad story of the Sleipner A.
2025: In the first hour, I hit the second example only 30 minutes in and ended 5 minutes early. For the second hour, I had only 5 minutes for the story of the Sleipner A.

Exam 1 draft due

Sept 10
Functions of several variables; Limits. Worksheet. Solutions.
Sept 11
Limit laws (§14.2); Continuity in several variables (§14.2); partial derivatives (§14.3). Notes.
HW 8 (Due Wed, Sept 16)

I get through page 6, but have to make conscious effort to keep the pace up. Typically start partial derivatives with 10-13 minutes left.
2025: I slightly shortened the limit laws discussion by only writing the quotient rule and started partial derivatives at the expected time.

Notes:
Having difficulty copying everything down in class? You can always fill stuff in from the lecture notes above.
The first midterm exam will be Tuesday, Sept 22 from 6:45–8:00pm.
See here for complete details, including how to register for the conflict exam.

Week 4

Sept 14
Applications of partial derivatives (§14.3 and §14.4). Notes.
Visualization: Heat equation.
HW 9 (Due Fri, Sept 18)

I cover everything except the proof of the first theorem at the bottom of page 5, but it's a little tight.

Sept 15
Functions of several variables; Limits. Worksheet. Solutions.

Exam 1 to printer.

Sept 16
Chain rule (§14.5). Notes.
HW 10 (Due Mon, Sept 21)

I drop the explicit error term on Page 3 and sometimes don't get through the "Alternate viewpoint" section. I suspect the whole derivation of the Chain Rule is too messy for them to get much out of; on the other hand, it is a nice of example of using linear approximation theoretically, which occurs frequently in these lectures. Perhaps one should derive the single-variable chain rule and then just talk about what happens for two variables in a more heuristic fashion.

Sept 17
The chain rule. Worksheet. Solutions.
Sept 18
More on the chain rule (§14.5), directional derivatives and the gradient (§14.6). Notes.
Visualization: Gradient and level sets.
HW 11 (Due Fri, Sept 25)

I cover everything in the notes and the lecture is a nice length.

Notes:
The first midterm exam will be Tuesday, Sept 22 from 6:45–8:00pm.
See here for complete details, including how to register for the conflict exam.

After the due date of a homework assignment, click the "VIEW ANSWER KEY" button at the top to see a complete worked solution to every problem.

Week 5

Sept 21
More on the gradient (§14.6) and overview of optimization (§14.7–14.8). Notes.
HW 12 (Due Mon, Sept 28)

This lecture is a nice length and I was able to get through it all without working too hard.

Sept 22
The chain rule. Worksheet. Solutions.
Midterm the First: 6:45–8:00pm.
Sept 23
No class.
Sept 24
No discussion section.
Sept 25
Local min and max (§14.7). Notes.
HW 13 (Due Wed, Sept 30)

This was fine when I skipped any detailed discussion of why x^3 is unstable. I finished page 4 at 30 minutes in with 10 minutes left for each of pages 5 and 6.

Notes:
Different tutoring and office hours this week.

Week 6

Sept 28
Absolute min and max (§14.7). Notes.
HW 14 (Due Fri, Oct 2)

I skip the asides on page 5 and have about 10 minutes for the example on page 6.

Sept 29
Taylor series, the second derivative test, and changing coordinates. Worksheet. Solutions.
Sept 30
Constrained min/max (§14.8). Notes.
HW 15 (Due Mon, Oct 5)

This lecture is a good length. There is time at the end to discuss why the local max in the last example is the absolute max, as outlined on page 6. I don't usually cover the bottom part of page 6.

Oct 1
Taylor series, the second derivative test, and changing coordinates. Worksheet. Solutions.
Oct 2
Introduction to space curves (§13.1–4). Notes.
Visualization: Cycloid.
HW 16 (Due Wed, Oct 7)

This is fine, I usually finish the examples and cycloid discussion at 25 minutes in.

In detail, this is §13.1, the first subsection of §13.2 (through page 849), the first subsection of §13.3 on arc length (through page 855.5), and §13.4 through page 863.

Week 7

Oct 5
More on arc length (§13.3) and integrating functions on curves (§16.2, pages 1063–1065). Notes.
HW 17 (Due Fri, Oct 9)

This is fine. I needed about 15-16 minutes to do everything after "Understanding these integrals"; once I did it in 13 minutes which was kinda tight.

Oct 6
Curves and integration. Worksheet. Solutions.

Should learn date of final now.

Draft of Exam 2.

Oct 7
Vector fields (§16.1) and integrating them along curves (§16.2). Notes.
Example vector field: Live wind map
HW 18 (Due Mon, Oct 12)

This lecture is a good length. I start page 4 with about 20 minutes left and need 8 minutes to cover the last example comfortably.

Oct 8
Curves and integration. Worksheet. Solutions.
Oct 9
More on integrating vector fields along curves; the Fundamental Theorem of Line Integrals (§16.2 and §16.3). Notes.
HW 19 (Due Wed, Oct 14)

In the first hour, I did everything and in the example on page 5 added a discussion of why we should expect the answer to be positive geometrically based on the first half of the lecture. In the second hour, I had to drop the "by hand" part of the calculation on page 5. In both hours, I started the discussion of the Fund Thm of Line Integrals with 20 minutes left.

Notes:
The second midterm exam will be Tuesday, Oct 20 from 6:45–8:00pm.
See here for complete details.

Week 8

Oct 12
Conservative vector fields I (§16.3). Notes.
HW 20 (Due Fri, Oct 16)

Sometimes I've managed to do everything except the last example on page 6 (F = 1/(x^2 + y^2) (-y, x)), but other times I've strugged just to get through stating Theorems A and B (which one definitely needs to do).
2025: I had the second experience both times, but the mic was out.

Oct 13
Integrating vector fields. Worksheet. Solutions.

Exam 2 to printer.

Oct 14
Conservative vector fields II (§16.3). Notes.
HW 21 (Due Mon, Oct 19)

As written, this lecture is a little short. I pad it out with a discussion of why averages over shorter and shorter paths converged to the value of the function at the fixed endpoint, but even then I sometimes end a little early. This is among the most theoretical lectures of the whole semester.

Oct 15
Integrating vector fields. Worksheet. Solutions.
Oct 16
Intro to multiple integrals (§15.1). Notes.
HW 22 (Due Fri, Oct 23)
Last day to drop the course (*)

This is fine.

Notes:
The second midterm exam will be Tuesday, Oct 20 from 6:45–8:00pm.
See here for complete details.

(*) Unsure whether to drop Math 241? Try taking one of the practice tests for the next midterm under timed conditions to see how you’re doing.

Solutions to all discussion worksheets are posted on Canvas under Files.

Week 9

Oct 19
Integrating over more complicated regions (§15.2 and §15.3). Notes.
HW 23 (Due Mon, Oct 26)

I get through these notes as written. In 2019, got to polar coordinates with 20 minutes left.

Oct 20
Multivariable integrals. Worksheet. Solutions.
Midterm the Second: 6:45–8:00pm.
Oct 21
No class.
Oct 22
Multivariable integrals. Worksheet. Solutions.
Oct 23
Polar coordinates (§15.3) and applications (§15.4). Notes.
HW 24 (Due Wed, Oct 28)

I cover everything, though I need 25 minutes to do the "Applications of Integration" properly and usually only have 20, resulting in some rushing at the very end.

Notes:
Different tutoring and office hours this week.
Solutions to all discussion worksheets are posted on Canvas under Files.
The final exam time should be announced by now.

Week 10

Oct 26
Triple integrals (§15.6). Notes.
HW 25 (Due Fri, Oct 30)

This lecture is fine, even with an extended answer to the question that always comes up, namely is why phi only goes from 0 to pi. I need at least 15 minutes to do "Alternate coordinates" section (bottom of page 4 to end).

Oct 27
Transformations of the plane. Worksheet. Solutions.
Oct 28
Integrating in cylindrical and spherical coordinates (§15.7 and §15.8). Notes.
HW 26 (Due Mon, Nov 2)

I skip the straightforward calculation of the integral on page 3, and usually finish the cylindrical example at 27-30 minutes in. If time remains at the end, I give a brief discussion of what slices look like in spherical coordinates.

Oct 29
Transformations of the plane. Worksheet. Solutions.
Oct 30
Changing coordinates I (§15.9). Notes.
HW 27 (Due Wed, Nov 4)

I skip talking about linear approximation (bottom of page 5 to end) and instead give a brief discussion of how the average of x - y over the triangle R is thus 1/3 and why that makes geometric sense.

Week 11

Nov 2
Changing coordinates II (§15.9). Notes.
HW 28 (Due Fri, Nov 6)

I always skip the indiciated pages 4 and 7, though I will state the aside on page 7 if there is time. While personally I find the discussion of linear approximation for functions from R2 to R2 very satisfying, my guess is that it goes over their heads given how little exposure they have had with linear transformations.

Nov 3
Integrating by changing coordinates. Worksheet. Solutions.

Exam 3 draft due

Nov 4
Surfaces in R3 (§16.6). Notes.
HW 29 (Due Mon, Nov 9)

This lecture is fine, even with the 5 minutes at the beginning for the general 3D change of coordinate formula.

Nov 5
Integrating by changing coordinates. Worksheet. Solutions.
Nov 6
Area and integration on surfaces (§16.6 and §16.7). Notes.
Visualization: Cones.
HW 30 (Due Wed, Nov 11)

For the "last time" part, instead of the example of the torus in the notes, put up the unit sphere, including the formulas for r_theta and r_phi. By condensing some of the calculations, I was able to get through these notes in 40-44 minutes, with the remaining time used to discuss the visualization; the latter is better with 10 minutes.

Week 12

Nov 9
Green’s Theorem (§16.4). Notes.
HW 31 (Due Fri, Nov 13)

This lecture was fine, maybe even a little short.

Nov 10
Green's Theorem. Worksheet. Solutions.

Exam 3 to printer.

Nov 11
Green’s Theorem and conservative vector fields in 2D (§16.4), but mostly flux in 2D (§16.5). Notes.
Visualization: Flux and flow.
HW 32 (Due Mon, Nov 16)

2016: This lecture is too long as written, even assuming all the "previously" bits are up before the starting bell rings. I skip worrying about non-simple curves in the "proof" of Green's Theorem (Case 2), and only do the bit of page 6 where I derived the formula for the normal vector from the velocity vector.

Nov 12
Green's Theorem. Worksheet. Solutions.
Nov 13
The Divergence Theorem in 2D (§16.5-16.9). Notes.
HW 33 (Due Fri, Nov 20)

I usually cover the the first five pages, though typically with only 5 minutes for the part after the separator. Sometimes, I only get to the separator, and I never do page 6.

Notes:
The third midterm exam will be Tuesday, Nov 17 from 6:45–8:00pm.
See here for complete details.

Week 13

Nov 16
Surface integrals of vector fields and the divergence theorem in 3D (§16.7 and §16.9). Notes.
HW 34 (Due Wed, Dec 2)

HW due Dec 2 instead of Nov 30 so everyone gets to do the next worksheet before it is due.

I just cover the first four pages, skipping the application about heat flow entirely. If one has a five minutes at the end, one could redo the solid cone example with another vector field, e.g. (x, 0, 0) or the easier (0, 0, z) so that the divergence theorem tells us we are computing the volume.

Nov 17
No discussion section.
Midterm the Third: 6:45–8:00pm.
Nov 18
Parameterizing the real world: surfaces in computer-aided design. Notes. Lecture video.
Visualization: Bezier curves and surfaces.
Online visualization: Bezier curves.
HW: None
Nov 19
Surface integrals of vector fields. Worksheet. Solutions.
Nov 20
No class, but HW 33 is due.
Notes:
Different tutoring and office hours this week.

Week 14

Nov 30
Stokes Theorem (§16.8), including the definition of the curl (§16.5). Notes.
HW 35 (Due Fri, Dec 4).

This lecture is much longer than it looks. I made one change: moved computing the curl of the vector field in the example, namely F = (-y, x, yz), forward to page 2 since it's more generic than than F = (y, 0, 0), which I also did. Only putting the top half of the first page on the board to start, I hit the top of page 4 with only 10 minutes left both times, which is tight even skipping the bit at the end about the lower hemisphere.

Dec 1
Surface integrals of vector fields. Worksheet. Solutions.
Dec 2
More on Stokes Theorem (§16.8), including understanding the curl (§16.5). Review of conservative vector fields. Notes.
HW 36 (Due Mon, Dec 7)

This lecture is a good length.

Dec 3
Stokes’ Theorem. Worksheet. Solutions.
Dec 4
Conservative vector fields in R3 (§16.8); Topology 101. Notes.
HW 37 (Due Wed, Dec 9)

2016 and 2018: This lecture was a fine length. 2019: In the first hour, I almost ran out of material; in the second hour, I didn't quite get through it all. Both results were fine.

Week 15

Dec 7
Electrostatics and Gauss’s Law. (§16.9) Notes.

This lecture is intensionally short to allow time for them to fill out the (son of) ICES survey. I completely skip the calculation of div E on page 2, and then it takes 42-43 minutes with some discussion of the second half of the last page.

Instructors should do Son of ICES today.

Dec 8
Stokes’ Theorem. Worksheet. Solutions.
Dec 9
Maxwell’s equations. Notes.

Skipping the second half of page 2 and simplifying Ampere's law to the case when the current is 0 made the notes as written take 35 minutes, leaving 15 minutes for a stirring summary the integral theorems and a hint at the general form of Stokes' Theorem.

Dec 10
Reading day.
Dec 11
Finals start.

Week 16

Dec 14
Monday
Dec 15
Tuesday
Dec 16
Wednesday
Dec 17
Thursday. Last day of finals.

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