Math 21a, Fall 2008
Frequently asked questions of Math 21a Fall 2008
FAQ
 Question: Answer: Question:On a couple of the problems in practice exams I was able to solve the problems without using some of the more advanced multivariable calculus methods we've learned Can we assume that any correct method of solving the problem will be given full credit on an exam? Answer: If you get through with an other method and everything is 100% correct, we give full credit. This is sometimes possible, like in Lagrange problems. But there are often pitfalls. You might get the right result with single variable methods, but these solutions are in general wrong or incomplete because boundary conditions are forgotten. Then graders often do not give any credit, not even partial credit. In general, we do not advise to be "sneaky" in exams (not only in mathematics). It is not appreciated and alternative solutions (even if clever) are often not recognized by graders because of the time constraints they have with grading. If you have time in the exam, you can do both methods to check your answer. We try to avoid solutions, where alternative methods are successful. Most of the time, alternative solution methods just are much more complicated or lead to a trap and most graders do not give any partial credit for solution attempts with a shortcut which does not work. Question:I love the pictures Mathematica can make, and want to make myself a desktop wallpaper from them. Do you know if there's a way of setting the size of the output image? Answer: ``` S=Plot3D[Sin[x y],{x,0,5},{y,0,5},Background->RGBColor[0,0,0],Boxed->False,Axes->False] Export["image.jpg",S,"JPG",ImageSize->{1600,1200}] ``` would produce a nice background picture for a 1600x1200 pixel monitor. Question:How do I submit a question to this FAQ list? Answer: Just send an email to math21a@fas or knill@math.harvard.edu or ask a section leader. If we see the question repeated, we will post it. Question:Which ISBN does the book have? Answer: Stewarts Multivariable Calculus Concepts and Context 3: ISBN 0-534-41004-9 But be careful.