nm

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These are replies submitted by nm

@Seb1123 

if it is any help, mathematica also can't solve it. It gives warning message

ode=y''''[t]+10*y''[t]+169*y[t]==0
bc={y[0]==0,y'[0]==1,y[Infinity]==0};
DSolve[{ode,bc},y[t],t]

   {}

 

DSolve::bvlim: For some branches of the general solution, unable to compute the limit at the given points. Some of the solutions may be lost.

In Maple, you can see something similar as follows

restart;
diffeq := diff(y(t),t$4)+10*diff(y(t),t$2)+169*y(t)=0;
bc:=y(0)=0, D(y)(0)= 1;
sol:=dsolve({diffeq,bc},y(t));
limit(rhs(sol),t=infinity);

Which gives  "UNDEFINED"

 

@Seb1123 

A 4th ODe does not need 4 boundary conditions

At school the teacher told us that an nth order ODE needs n boundary/or initial conditions for complete solution. If you do not provide these, the solution will contain constants of integrations instead. Since you have 4th order ODE, but you only supplied 3 conditions. That is why I said you probably need another conditions to fully satisfy the ODE.

btw, I do not see anything wrong with the syntax you used. When maple returns nothing it means it can't figure how to solve the ODE with these boundary conditions.

 

4th order ODE needs 4 boundary conditions?

dsolve({diffeq,y(0)=0,D(y)(0)=1,D(y)(infinity)=0},y(t)) 
Returns nothing.

May be becuase the boundary conditions at infinity makes Maple not able to find a solution?

 

@vv 

Thanks but Iam little confused about how is this suposed to be used. Does one have to supply value at which these function evaluate? How does one know which x,y values to use? For example

facxy(1/(x-1)*y,x=1,y=1);

Here it is separable. {  1/(x-1)  , y }   I picked say x=1,y=1 but this gives

    Error, (in facxy) numeric exception: division by zero

How is user supposed to figure what x,y to use? if I pick x=0, but later do

facxy(1/x * y,x=0,y=1);

Same problem shows up. I do not know in advanced what the functions are.

 

 

@Mac Dude 

"It isn't quite clear to me why you would want to do that, but of course there maybe perfectly valid reasons I just haven't encountered yet. "

In cases when a proc() wants to construct a mathematical expression, which uses symbol not passed by user. Consider for example dsolve. It returns constant of integration. Maple calls that _C1, _C2. etc... These symbols were not passed in by user.

One can carry this for more symbols than just _C1...

Thanks for the hint about exporting the symbols. This is useful. I only use simple proc() now and not advanced enough to use modules yet.

@Kitonum 

Thanks. But this does not work on all cases. For example

Separation( exp(x+y))  should return [exp(x), exp(y)]

I'd also like it to separate sqrt(x*y) to sqrt(x)*sqrt(y) with ofcourse the assumption that both x,y are positive. But your function is still very useful.

 

Do not use 2-D Input mode.

It is not Maple code.

Stick to using pure Maple code.

@vv 

I see. So Maple moved the whole 3*(y^2+1) to the left side. Ok. No problem. But then why it did not do the same for y'=3*x*y^2  case? Since one can't write Latex here, I attach image

So following same logic, I would expect Maple to give solution y=-1/(x^3+3c). 

Again, both solutions are correct. But I was trying to see if I figure what Makes Maple decides which terms to separate.

 

@Rouben Rostamian  

I've corrected hand solution. I should have tested with more functions :)

@Rouben Rostamian  

Why numerical solution when it can be solved analytically?

sol:=pdsolve([pde,Bcs,ics],u(t,x)); 

sol := u(t, x) = sin(x)*exp(-t)

@tomleslie

"fopen() is successful so carry on. Why/what would you check?"

humm... How would you know fopen() was successful in first place in order to "carry on"? That was my question. Maple help does not show one single example of how to check and what to do. It just says fopen raises an error. Ok. How does one know this in a script?

No eyes. Non interactive.

Imaging one is blind. How would they know fopen has failed? Also imagin one is also deaf so the can't hear an error beep coming when an error is printed on screen. That is what I am asking.

You showed one method is to use trap. Ok. So one should not check fd? Is using trap/catch the official method to check for fopen failing? Is this documented any where? I have not seen one example in Maple help using fopen() doing any check on status of the open. Using trap or otherwise. But if using trap is the correct way in Maple to check for fopen, I have no problem using it.

 

@vv 

" the argument of value should be a label; you have probably unchecked "Show equation labels" In Tools > Options > Display. But even so, value(...) executes correctly after pressing Enter. "

That is correct. I turned off labels. Labels are stupid way to write software. So I turned it off. I do not use labels. I do not want to see labels. I want to just see plain old fashioned Maple code in front of me.

But even if I turn lables on. How is this going to help me? I still can't copy paste the command from the help page to my Maple worksheet.

Maplesoft wants to push 2D and document mode on us. They can keep Maple then. I am done with Maple. There are other software to use.

 

 

This has been asked for 100 times. Maple simply wraps things to fit the window with. There is no option in Maple make it not do this.

 

Maplesoft is busy with making cloudy things to have time to fix this basic usability issue.  see for example

http://www.mapleprimes.com/questions/220807-How-To-Make-Maple-Worksheet-Display

http://www.mapleprimes.com/questions/222218-Prevent-Long-Line-Wrapping-Split-GUI

 

One solution is to buy an ultra wide monitor. LG has 34" ultra wide monitor for sale at costco now for only $330. 

Maple have many other basic usability issues. Too long to list here.

 

@vv 

Thanks for the test. Little over my head. But you say

" convert does not replace a space by \n; it simply inserts some \n 's. "

But why?? That is the question. When one calls a function to convert expression to string, one does not expect the function to mess up with the input and inserts nilly willy extra characters in the string generated such as carriage returns.

I do not see how this is supposed to be OK. But again, I am no Maple expert. I am just talking common sense and from software design point of view. This behavior is not something one would expect.

And thanks again for the help.

@vv 

Thanks! This seems to have fixed it in my first test.

But I really have no idea what is going on. How can convert an expression to a string replace a space by \n? And is considered OK? I do not get it and I do not understand the logic behind it.  Maple does some really strange things.

Thank you

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