awass

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16 years, 285 days

MaplePrimes Activity


These are questions asked by awass

When I call up a Help page I see mostly boxes with question marks inside. If I copy the page into Word I get a badly formatted document in Canbria font. On other pages I get a font drop down box that indicates the page is in DejaVu Sans font and if I then change that to some font on my system (MAC 10.12.1) I get a perfectly readable document. Is there some preference, startup code or setting I can change to fix this annoyance?

The following program hangs on the last command and a hard restart is required. The computation of a 2 x 2 matrix times a 2-vector is not that hard. Any ideas as to what is happening?

Another question: if v is a vector that depends on x and y say why does
>solve(v=0,{x,y})
not work?

It should only take a few lines of code to change v=0 to the system {components of v = 0}

Frequently a variable appears in an expression but not in the result, e.g., there is no x in int(sin(x),x=0..3). How do I tell that to Maple? I am trying to solve (numerically) an ODE of the form
x^2 y'' + alpha(x) y' +   beta(y) = 0. However, alpha(x) has an integral in its defintion whose upper limit is x. Maple demands that I list the dummy variable of the integral as a parameter. How do I deal with that? BTW, Maple has no problem with plot (alpha(x), x=0..6) for example.

I have 2 questions.

 

1) The help pages discuss the use of functions described by piecewise when using dsolve. The examples are clear enough but nothing is said about using the numeric option and piecewise. I get an error message for a very simple example: y' +R(t) y^2 = 0. Are I correct in assuming that dsllve numeric cannot deal with piecwise continuous functions?

2) I tried to solve a system of 2 second order constant coefficient linear ODEs using dsolve. After a very long wait (over an hour) I gave up. I tried again using "method=laplace" and got an instant answer. I did not bother to mention it here but it occurred again, this time with a fourth order and second order constant coefficient system. Very strange! I know that the laplace transform is a very useful tool; shouldn't Maple also know that?

I  often find mself in the following quandry: I am investigating a problem, I do a few examples, run a do loop for j from1 to 5 to see if that works and then enter

for j from 1 to 200 do  a[j]:=blah, blah,...  end do:

and 15 minutes later nothing has happened. Is the loop finishing up with j = 198 or so or is it stuck at j = 23 and it will take forever to finish? Or perhaps there is an error that turns up for j > 23?

When I think about it I can insert a print(j) command to keep track of this but there are other situations where that doesn't work. For example,

Order := 35; mtaylor(....

When nothing happens is that because the calculation is almost done? or stuck? etc.

Is it possible to take a quick peek at the state of Maple and the decide whtether to continue the computation or abort? If the calculation of mtaylor(... is particularly long I might settle for the 15 coeficients computed so far rather than abort. Can I get at those?

Any advice?

 

 

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