Harvard University,FAS
Fall 2005

Mathematics Math21a
Fall 2005

Multivariable Calculus

Course Head: Oliver Knill
Office: SciCtr 434
Email: knill@math.harvard.edu
Harvard Mathematics

Weekly checklists: "Somewhere, over the rainbow ..."
Week1 Week2 Week3 Week4 Week5 Week6 Week7 Week8 Week9 Week10 Week9 Week10

Homework

All sections have the same homework during weeks 1-10. Biochem homework will be different in weeks 11-12. Here are scanned versions of the problems in Rozanov. If you solve other problems from the book to prepair for the exam, look here.
  • Homework is due at the beginning of class.
  • Please staple your homework.
  • No late homework accepted but will delete the least 3 scores (that is one week of HW for MWF sections and one week of HW for TTh sections). Reserve these 3 "Joker" cards for emergencies.
    Students who can not be in class October 2-3 due to Roshe Shana have the option to turn in the homework with their next homework at those days. The same applies for the Yom Kippur holiday, which is Thursday, October 13.
  • Collaborations are welcome however you must turn in your own copy and list on it the names of your collaborators.
  • Please write legibly and indicate clearly, where a new problem starts.
  • Try to keep the problems in order.
  • Use words to explain your work, if necessary. Show your work.
  • If unable to finish a problem, indicate where you are stuck. This will help us to give partial credit.
  • Please infom about typos, misprints. We state here corrections to the in class distributed texts as well as to the posted solutions. Each hint gives you a bonus point. The texts posted here are corrected.
  • (+Sol) means solutions have been posted. Solution folder (in case, solutions are not yet linked).

Week 1:

1. Class 9.1: 8,10,14,16,18           Due Wed Sep 28  Sol
2. Class 9.2: 16,22,38  9.3: 34,38    Due Fri Sep 30  Sol
3. Class 9.4: 4,14,16,26,30           Due Mon Oct  3  Sol
Tuesday/Thursday section (this is a suggestion, the 
section leader might split differently)

1. Class 9.1: 8,10,14,16,18, 9.2: 16  Due Thu Sep 29  Sol
2. Class 9.2: 22,38  9.3: 34,38         
         9.4: 4,14,16,26,30           Due Tue Oct  4  Sol
Week 2:

1. Class 9.5: 6,32,34,48,54           Due Wed Oct 5  Sol
2. Class 9.6: 2,4,10,14,24            Due Fri Oct 7  Sol
3. Class 9.6: 12,22,34                Due Wed Oct 12 Sol
         Problem A: What surface does the equation 
         $x^2-6x-y^2-2y+z^2-8z + 26=0$
         represent? 
         Problem B: Find the diameter of the surface
         S: $100 x^2+30 y^2+25 z^2 = 1$.
         In other words, what is the maximal
         distance of two points P,Q on S?     Solutiosn AB
                                              (LaTeX)
Tuesday/Thursday section (this is a suggestion, the
section leader might split differently)

1. Class 9.5: 6,32,34,48,54           Due Thu Oct 6  Sol
         9.6: 2,4                                   
2. Class 9.6: 10,14,24                Due Tue Oct 11 Sol
         9.6: 12,22,34, Problem A,B   Solutiosn AB
                                      (LaTeX)
Week 3:

Due to Columbus day, no class on Monday           
1. Class 10.1: 14,34,38               Due Fri Oct 14  Sol
         10.2: 28,36 
2. Class 10.3: 2,14,18                Due Mon Oct 17  Sol
         10.4: 6,24 (more info to problem 10.4.24)
Tuesday/Thursday section:

1. Class 10.1: 14,34,38               Due Thu Oct 13  Sol
         10.2: 28,36 
2. Class 10.3: 2,14,18                Due Tue Oct 18  Sol
         10.4: 6,24 (more info to problem 10.4.24)
Week 4:

Monday is review, no homework assigned due to midterm
1. Class 9.7:   10,18,20,32,36        Due Fri Oct 21  Sol
2. Class 10.5:  4,18,28,30,32         Due Mon Oct 24  Sol
Tuesday: one hour review. The section leader might package the
assignments differently:

1. Class 9.7:   10,18,20,32,36        Due Thu Oct 20  Sol
2. Class 10.5:  4,18,28,30,32         Due Tue Oct 25  Sol

Week 5:

1. Class: 11.1:22 11.2: 36 11.3: 12,64,66  Due Wed Oct 26   Sol
2. Class: 11.3:68,72,74,80,                Due Fri Oct 28   Sol
          A: Verify that f(x,t)=exp(-r t) sin(x+ct)
          satisfies the advection equation
          ft(x,t) = c fx(x,t) - r f(x,t). 
3. Class: 11.4: 2,4,26,30,32                 Due Mon Oct 31   Sol

Tue/Thu: (might be split differently in your section)

1. Class: 11.1:22 11.2:36 11.3:12,64,66,68 Due Thu Oct 27  Sol
2. Class  11.3:72,74,80,    and Problem A                  Sol
          11.4:2,4,26,30,32                Due Tue Nov  1
Week 6:

1. Class: 11.5: 2,32,28,26,36              Due Wed Nov  2  Sol
2. Class: 11.6: 24,42,44,A,B               Due Fri Nov  4  Sol
     A: r(u,v) = (u,v2,u2+v2) is a parametrized surface S.
        a) Find an implicit equation g(x,y,z)=0 for this surface.
        b) Use Aa) to find the tangent plane at the point (1,1,2).
     B: a) Why are the vectors ru(u,v) and rv(u,v) tangent to the S?
        b) Use Ba) to find the tangent plane at the point (1,1,2) again. 
3. Class: 11.6: 8,26,28,36,46              Due Mon Nov  7  Sol
Tue/Thu: (might be split differently in your section)

1. Class: 11.5: 2,32,36,26,28              Due Thu Nov  3 Sol
          11.6: 24,42
2. Class: 11.6: 44,A,B            
          11.6: 8,26,28,36,46              Due Tue Nov  8 Sol

Week 7:

1. Class: 11.7: 2,10,12,44,48              Due Wed Nov   9 Sol
2. Class: 11.8: 4,6,10,16,18               Due Mon Nov  14 Sol
There is no class on Friday due to Veteransday
Tue/Thu: (Try to do all the problems for Thursday! Nov 15 is the exam. 
          It is important to do those problems before the exam.)

1. Class: 11.7: 2,10,12,44,48              Due Thu Nov 10  Sol
2. Class: 11.8: 4,6,10,16,18               Due Tue Nov 15  Sol
Week 8:

1. Class: 12.1: 8, 12.2: 12,16,18,22       Due Fri Nov 18  Sol
2. Class: 12.3: 2,26,36,42,44              Due Mon Nov 21  Sol
Tue/Thu:

1. Class: 12.1: 8, 12.2: 12,16,18,22       Due Tue Nov 22  Sol
2. Class: 12.3: 2,26,36,42,44              Due Tue Nov 22  Sol
Week 9:

1. Class: 12.4:  8,20,24,28,30               Due Wed Nov 23 Sol
2. Class: 12.5:  2,22,  12.6: 2,24,28        Due Mon Nov 28 Sol
Tue/Thu:

1. Class: 12.4:  8,20,24,28,30                               Sol
          12.5:  2,22,  12.6: 2,24,28        Due Tue Nov 29  Sol
Week 10:

1. Class: 12.7: 4,12,32,44,48                Due Wed Nov 30 Sol
2. Class: 12.8: 4,8,16,32,36                 Due Fri Dec  2 Sol
3. Class: 13.1: 24,34 13.2: 18,20,42         Due Mon Dec  5 Sol
Tue/Thu:
1. Class: 12.7: 4,12,32,44,48                Due Thu Dec  1 Sol
2. Class: 12.8: 4,8,16,32,36                 Due Tue Dec  6 Sol
          13.1: 24,34 13.2: 18,20,42       

Week 11:

1. Class: 13.3: 6,16,22,26,28                Due Wed Dec  7 Sol
2. Class: 13.4: 2,8,12,14,18                 Due Fri Dec  9 Sol
3. Class: 13.5: 6,10,14,27,36                Due Mon Dec 12 Sol
Tue/Thu:
1. Class: 13.3: 6,16,22,26,28                Due Thu Dec  8 Sol
2. Class: 13.4: 2,8,12,14,18                 Due Tue Dec 13 Sol
          13.5: 6,10,14,27,36        

Week 12:

1. Class: 13.6: 20,22,38,40,42               Due Wed Dec 14 Sol
2. Class: 13.7: 2,8,10,14,18                 Due Fri Dec 16 Sol
3. Class: 13.8: 2,10,24  13.9: 34,38         Due Mon Dec 19 Sol

   Problem 13.8:24:    replace 2x+2y+z2 by    2x i + 2y j + z2 k 
Tue/Thu:
1. Class: 13.6: 20,22,38,40,42               Due Thu Dec 15  Sol
2. Class: 13.7: 2,8,10,14,18                 Due Tue Dec 20  Sol
          13.8: 2,10,24  13.9: 34,38  

   Problem 13.8:24:    replace 2x+2y+z2 by     2x i + 2y j + z2 k 

Week 11 (biochem):
1. Class: Rozanov: 1.1, 1.2, 1.4, 1.10, 2.1, 2.5, 2.6, 2.14  Due Wed Dec 7 rsp. Thu Dec 8 Sol
2. Class: Rozanov: 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7         Due Fri Dec 9 rsp  Tue Dec 13Sol
3. Class: Rozanov: 4.11, 4.12, 4.13, 4.14, 4.15              Due Mon Dec 12 rsp Tue Dec 13Sol
Week 12 (biochem):
1. Class: Rozanov: 3.1, 3.2, 3.4, 3.8, 3.13, 3.14, Problem A,B* Due Wed Dec 14 rsp Thu Dec 15 Sol
2. Class: Rozanov: 5.1,5.2,5.3,5.4,5.5,5.7,5.8                  Due Fri Dec 16 rsp Tue Dec 20Sol
3. Class: Rozanov: 5.14 and 5.16                                Due Mon Dec 19 rsp Tue Dec 20Sol
Problem A: Monty Hall Problem: A contestant plays the following game. He or she is presented with three doors. Behind one door is a prize and behind the other two doors are goats. We assume that the contestant prefers the prize to the goat. The contestant picks a door behind which he or she expects to find the prize. Monty Hall, the game show host (who knows where the prize is), opens one of the two other unpicked doors, revealing a goat. The contestant is now given the option of switching his or her choice to the other closed door.

(a) Should the contestant switch?
(b) What if Monty Hall doesn't know where the prize is but picked a random door which happened to have a goat behind it?
Sol.
Problem B: Two Envelopes Problem. ((* no need to submit a solution to this problem)
John has two envelopes containing X and 2X dollars respectively. He gives one envelope to Jack and one to Jill (which envelope is decided by the flip of a fair coin). Jack opens his envelope and sees Y dollars. He concludes that Jill's envelope contains 2Y or Y/2 dollars with equal probability (since Jack has probability 1/2 of getting the envelope with more money). He calculates that the expected amount of money in Jill's envelope is E(Jill's envelope) = 1/2(2Y + Y/2) = 5Y/4 > Y. So Jack expects Jill's envelope to contain more money. At the same time, Jill performs the same calculation (both are Math21a biochem students) and expects Jack's envelope to contain more money. So they agree to swap envelopes, both expecting to get more money. Is there anything wrong with this argument? Should we expect the total amount of money in the 2 envelopes to increase after swapping? Is this a way of solving the world's financial problems? Sol.
Please send comments to math21a@fas.harvard.edu Background music: Pictures at an Exhibition" by the Russian composer Modest Petrovich Mussorgsky.
Math21a, Multivariable Calculus, Fall 2005, Department of Mathematics, Faculty of Art and Sciences, Harvard University


Sat Jan 21 22:11:28 EST 2006