## stop_cond question...

I am using dsolve to integrate a system of equations, and I am using stop_cond to stop the integration when certain conditions are met.

The problem is, I want the integration to stop when condition 1 AND condition 2 are met, but when I use, for example

stop_cond=[y(t)-2,t-4]

it stops as soon as ONE of these conditions are met, not both. I want it to stop when y(t) is equal to 2 AFTER t=4, not before.

Any suggestions would be greatly appreciated!

## nice looking superscripted Arrows ?...

Hi, i just want to write this equation im Maple,  how do i do it ?

thanks

## Solving systems of polynomial equations...

Hi

I'm trying to find all solutions to a system of polynomial equations. I've tried using Isolate from the RootFinding package and for some choice of parameters this works well. However changing the parameters (i.e changing some of the coeffients of the polynomials), I get the error message.

Error, (in RootFinding:-Isolate) decreasing address previous=1e0f0020 new=10010020!

Any ideas on what this means?  possible ways around it? or other functions in maple that would give me all solutions?

Thanks, Steve.

## color function in plot3d...

I am trying to color  3D plots according to phase using color=argument(x)/Pi/2

I get different results depending on the form I enter the expression x, as shown on the worksheet. Any suggestions to make this consistent?

## Broken help links / Maple 12 Classic

by: Maple
```I am missing the F1-help to work properly after highlighting words
at least for the following

invfourier ---> completely missing (it is in inttrans)
invlaplace ---> completely missing
invmellin  ---> completely missing
fourier    ---> MTM[fourier], but not inttrans

Parts      ---> completely missing (expect it in IntegrationTools)
Flip       ---> ImageTools[Flip], but not...```

## How does Maple find limit and how to define/assume...

I was testing if Maple can prove/show limit(a*(1-F(a)), a=infinity,left)=0, where F(.) is a general cumulative distribution function. Though, I doubt Maple has the ability.  However, I come across with some other questions during the exploration:

1. how is maple exactly doing to find limit:
Let's first try a normal distribution case:

with(Statistics):
U := RandomVariable(Normal(s,t))  :
limit(CDF(U,x),x=infinity,left)  assuming t>0,t<infinity ;

## Paragraph styles - some won't work...

Is there an explanation on how each of the different paragraph styles work?

I was experimenting the other day and some selected paragraph styles don't allow you to type any text at all.  Couldn't find anything in the help pages, or I might have just been looking in the wrong area.

## MY MAPLE WORKSHEET IS VERY VERY VERY SLOW: can you...

Hi to everybody.  I have to manipulate a system of partial differential equation,one by one.I have in particolar to derive a lot of time my differential equations(shallow water equations),and then to group, to substitute and at the and I need time derivative in function of spatial derivative.

I'm almost done. The problem is that now every time that  I execute a command it takes  a lot of time. The entire file takes some minuts to compile. It's so slow.

## Runge-Kutta of order 2 does not evaluate...

Hi all,

Suppose that you want to solve x'(t)=f(x,t)   x(t0)=x0

The theory show that:

x(t+h)=x(t)+1/2*h*(F1+F2) where F1=f(x,t) and F2=f(x+F1,t+h)

## implementing switch/case?...

Is there a switch/case statement in Maple?  So that instead of:

if (a = a1) then

b1

elif (a = a2) then

b2

elif (a = a3) then

b3

end if

Something like:

switch (a) {

case: a1 {b1}

case: a2 {b2}

case: a3 {b3}

}

???

I'm potentially going to have a long list of elif's and might need  more efficient way of doing it.

## 3dplot...

How do I plot a 3d helicoid?  I can easily plot a helix, but cannot figure out how to fill the plane to the axis, to generate the helicoid?

Leslie

## Building a Set

by: Maple

I recently discovered a minor variation on the technique of building a set using a table. The purpose for using a table rather than inserting new items directly into a set is that, in a loop, the latter technique is O(n) rather than O(n).  The way I would normally do this is to assign a counter and an empty table, and then, in a loop, compute the new element, increment the counter, and insert the element into the table at the counter index.  For example,

## Numerical solution of ODE with singularities...

Hi all,

while studying this ODE

## Filename generator

Maple

Ever wondered how you can create filenames by cycle.

Well, I did, because I needed it. And I came up with something that works and because once i forgot it, I decided this time to put it here. At least, I won't forget again :) If you have a better way to do it, please, say so.

The idea:

>A:=`/home/Data/file_`; B:=`.txt`;

>for i from 1 to 3 do C:=cat(A,i,B); writedata(`C`,[i],integer);od;

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