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Bart

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These are questions asked by Bart

Undefined integral of zero....

Bart 117 Maple 2019
integration undefined
April 19 2023
0 7

The following 2D integrals of 0 are seemingly trivial and one would expect them to evaluate to zero, but Maple evaluates them to undefined

int(0, x=0..infinity, y=0..1) # undefined
int(0, x=0..1, y=0..infinity) # undefined

When the 2D integral is split into two 1D integrals, it does evaluate to zero, as the following examples show

int(0,x=0..infinity) # 0
int(int(0,x=0..infinity), y=0..1) # 0
int(int(0,x=0..1),y=0..infinity) # 0

If infinity is replaced by a variable (say 'c'), the first two integrals are also evaluated to zero.

It may be connected by the following

int(a, x=0..infinity, y=0..1) # a*infinity
int(a, x=0..1, y=0..infinity) # a*infinity
int(a,x=0..infinity) # signum(a)*infinity

So for the 1D integrals the signum is applied to 'a' when the interval is infinite, but not for the 2D integrals. I'm not sure about this difference.

Issues with pdsolve (2)...

Bart 117 Maple
pde pdsolve differential-equations
May 21 2019
1 1

Hi,

There seems to be an issue with pdsolve, which is similar to https://mapleprimes.com/questions/222498-Issues-With-Pdsolve.

pdsolve([diff(u(x, t), t) = diff(u(x, t), x, x), u(x, 0) = 1, u(0, t) = 0, u(2, t) = 0]); # works

pdsolve([diff(u(t, x), t) = diff(u(t, x), x, x), u(0, x) = 1, u(t, 0) = 0, u(t, 2) = 0]); # swapped arguments, works

pdsolve([diff(u(x, t), t) = diff(u(x, t), x, x), u(x, 0) = 1, u(-1, t) = 0, u(1, t) = 0]); # translate by -1, works

pdsolve([diff(u(t, x), t) = diff(u(t, x), x, x), u(0, x) = 1, u(t, -1) = 0, u(t, 1) = 0]); # swapped arguments and translate by -1, doesn't work

The solution for the last example doesn't incorporate the initial condition correctly, while it is the same as the third example (except for swapped arguments). Not sure if this is still a problem in Maple 2019, though.

Problem with graphics when using eBookTo...

Bart 117 Maple 2018
pdf ebooktools
February 07 2019
0 2

Hi,

I'm using the eBookTools package to convert a .mw file as a chapter into a PDF file. However, a problem arises when I convert a document with a few repeated plotting commands (such as plot(x^2)). The issue is that in the final PDF the images of the various plots overlap, and that the individual plots can't be clearly seen. Is there a resolution to this?

Thanks,
Bart

Issues with pdsolve...

Bart 117 Maple 2016
pdsolve
August 11 2017
2 4

will give me

which is indeed a solution of the PDE1

will give me

which is not a solution of the PDE2

However, both differential equations are equal, only the arguments are swapped around. Am I doing something wrong, or is this a bug?

Thanks

Series with equation number bug?...

Bart 117 Maple 2015
series
February 09 2016
0 7

Hi,

When I execute the command

series(exp(x),x)

and then refer to the equation in a new execution group using a equation label (CTRL-L on Windows), the equation is shown in Maple 18, but in Maple 2015 I get an error message: 'Error, missing operator or ';'. Using the % instead does work for both versions.

Is this intended behaviour or a bug in Maple 2015?

Thanks,

Bart

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