Alex Smith

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16 years, 359 days

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These are answers submitted by Alex Smith

Another possibility is

cos*(beta-alpha);

If it's just for display, you could use something like Cos(beta-alpha) .

 

I never use the old system that seems to be underneath the top level Maple add-on.

For example, I would use

$a=maple("0");
$d=maple("0");
$b=maple("$a+($d)");

instead of your code.

 

OK-I sent an email to technical support and copied our system administrator so that the requested data will be sent.

I think the better banking analogy is this: Bank Customer A logs in to her account and transfers money from her savings account to her checking account, but does not close the browser.

Next Customer B comes along to the terminal, logs in to his account with his credentials, sees his name and accounts and feels confident that all is as it should be. He also elects to transfer money from his savings account to his checking account, only to find out indirectly that his money went into Customer A's checking account, and that he cannot readily document the error without having a bank official discover it on his behalf.

Then the bank blames Customer B for his bankruptcy because he is so naive as to not have started a new browser session.

 

The key point is that Student B did login to a MapleTA session with his credentials, and was presented with his version of the assignment, and not that of Student A.

 

 

 

We have continued having trouble with missing MapleTA 3.01 grades.

Today we just realized the following "bug."

Student A enters answers and gets their assignment graded. Without closing the browser, Student B logs in to MapleTA and enters answers for their assignments. It happens frequently that the grade record for Student B is missing in the MapleTA gradebook. It turns out that the grade shows in the record for Student A! So this is where the "missing" grades are ending up.

 

You can save the Maple worksheet as an rtf file, and then it is straightforward to convert rtf to pdf.

 

If you are going to do this without a package, I think you should start by calculating the Christoffel symbols. Here is the code I always use.

 

with(LinearAlgebra):
X:=Array([seq(x[i],i=1..4)]);
X:=Array([r,phi,theta,t]);
g:=Matrix( 1..4,1..4,shape=symmetric):

g[1,1]:=-r/(r-2*M);
g[2,2]:=-r^2;
g[3,3]:=-r^2*sin(phi)^2;
g[4,4]:=(r-2*M)/r;


gup:=MatrixInverse(g):


Gamma_Fill:=(a,b,c)->add(gup[a,i]/2*(diff(g[i,b],X[c])+diff(g[i,c],X[b])-diff(g[b,c],X[i])),i=1..4);

Gamma:=Array(1..4,1..4,1..4);

for a from 1 to 4 do
for b from 1 to 4 do
for c from 1 to 4 do
Gamma[a,b,c]:=unapply(simplify(Gamma_Fill(a,b,c)),X[1],X[2],X[3],X[4]):
od;
od;
od;

for a from 1 to 4 do
for b from 1 to 4 do
for c from 1 to 4 do
if Gamma[a,b,c](x[1],x[2],x[3],x[4])<>0 then
print(`Gamma`[a,b,c]=simplify(Gamma[a,b,c](X[1],X[2],X[3],X[4])));
fi;
od;
od;
od;

For your first question regarding

evalb( (x=5 or x=7)  implies (x^2 = 49));

notice that both (x=5 or x=7) and x^2=49 are false since nothing is assumed about x.

We know "False implies False" is "True".

Try plot3d( [r*cos(phi),r*sin(phi), f(r,phi)], r=a..b, phi=c..d)

where z=f(r,phi).

This is a special case of

plot3d( [x(u,v),y(u,v),z(u,v)],u=a..b,v=c..d);

Doug,

We have had a Microsoft exchange server for years, and have always had this problem with mw files.

For this reason, I use Classic in class even though I don't email files to students. This encourages students to do the same, and minimizes this problem somewhat. I warn them that if they use Standard, they will someday forget to zip the file before emailing it.

But it is a never ending nuisance.

 

 

Although the constant function is a solution, it seems possible that there might be other solutions. I don't think the uniqueness theorem for first order diffeqs. applies in this situation, does it?

Before you can use spacecurve, you need to load the plots package:

 

with(plots);

 

I had forgotten about this bug. I think it got fixed with 3.01. Below are excerpts of an exchange I had with technical support about this issue. The bottom line for the workaround: don't let students "print for offline work"  before they first (a)  "Quit and Save," (b) logout, and then (c) log back in. Then they can proceed with "print for offline work."

Excerpt from response from technical support:


We have been able to reproduce the problem you mention below with printing an assignment.  What we've found is that when a user starts a test and quits without saving their work by clicking "Quit and Save", the serialized version of their test is not written to the database.  If the user then logs out, logs back in and restarts the test, the same active test is used, but new versions of the question are chosen.


However, if the user restarts the test without logging out, or exits the test using "Quit and Save", then serialized versions of their questions are written to the database and they will always get these questions back.


This is a bug that will need to be addressed in a future update.  Thank you very much for bringing this problem to our attention.  For now the way to avoid the problem is to ensure the original data gets written to the database.  One way to do this is the method you suggest below.

Another is to ensure that users click "Quit and Save" when leaving an assignment.

........

Excerpt from my original message to technical support:


Another medium-serious bug in MapleTA 3.0 has come to my attention.
When a student brings up an assignment, they are presented with the option of
"Print for offline work" or "Work assignment online."


Some of my Calculus III students and I find that if one picks the print option, and then logs in >shortly< thereafter, then all is OK and as designed. Good.


But if the student waits a few hours before logging back in to the assignment, they are presented with different questions!

Disaster.

I think I have a work around, but I need to test it more.

This potential work around is to select "work the assignment online"

option first. Then select "Quit and Save". Next come back into the system, and then select the print option, and go from there as usual.
 

  I have had a handful of complaints from students that, when they have clicked on ‘grade’ on finishing an assignment, then they have been logged out and returned to the login page. When they have then logged in again, there is no record of that particular attempt at the assignment. This appears to be an intermittent, randomly occurring problem in a small minority of cases. We are sending log files to MapleTA as requested. Has anyone experienced such odd behaviour. We have rebooted but to no avail.

This drove me crazy for months. I asked technical support for help to no avail.

The about two weeks ago, I realized that on rare occassions, MapleTA registers some students as guests, and so their grade is not recorded. When a student reports this, go to the System Homepage, look under Adminster Users, find the student and change their role.

I pointed out the bug to technical support. Here was their reply:

"Yes, there was a problem in the previous version of Maple T.A. where students could be registered with the "guest" role.  This was one of the issues that was addressed in the current version of Maple T.A. (version 4.0)."

I thought it outrageous that they did not tell me this, especially since I reported the problem months earlier. We had a real rough transition from MapleTA2.5 to 3.0, and I have been reluctant to switch from 3.01 to 4.0.

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