## positive root of polynomial...

I have a real polynomial, p(x). I want to know only, if it has a positive root? Is it possible to answer this question without the sturm command?

## OpenMaple rtable creation and rts->foreign...

I am using OpenMaple (kv->rtableCreate or RTableCreate) to allocate large rtables which I then fill with data before returning to Maple. It seems to be slow. For example, a table with 120 Mwords takes 1 second to allocate and 0.640 seconds to fill. I suspect this is because the table is initialized to zero. I would like to skip this initialization and maybe use malloc to allocate the table, however I want it to behave like a normal Maple object (ie: garbage collected if not referenced, etc). The documentation says it is important to set rts->foreign to true, but it doesn't say why. Will this prevent garbage collection ? I would also like to know the purpose of rts->foreign.

## complex roots...

I read the help material for the roots command, but apparently don't understand it correctly. I've tried roots(x^2+x+1,I) and roots(x^2+x+1, complex) and the only thing returned is [ ]. How do I use the roots command to get complex roots? Thanks.

## solving a quartic...

When I enter solve(x^4-x^3+1) I get 4 RootOf place holder solutions. For example RootOf(_Z^4-_Z^3+1, index = 1). This is very frustrating because I'm trying to obtain answers not place holders, and I cannot figure out how to make Maple solve the problem. Is Maple perhaps trying to tell me that it cannot solve the problem? If not, how do I force Maple to return answers instead of place holders, on this and similiar problems? Just as there is the quadratic equation for obtaining solutions to second degree equations, I understand that there are standard equations for solving cubics and quartics so I would be surprized if maple cannot solve x^4-x^3+1 symbolicly.

## 'machine' epsilon...

```Working in usual programming languages there is a largest machine epsilon
with 1 + epsilon != 1.

Now I am working with floats in Maple and want something similar: given a
real constant x (as positive floating point number) and m:=floor(log10(x))
(= ilog10(x) scales the x (down or up) to be of size 1).

My question is:

Does the following always evaluate to "true"

x + epsilon = x; evalf(eval(%, epsilon= 1/10^(Digits-m)));

and to "false" if taking m+1 instead?

Sorry, stupidly can not find the answer in the docu ...
```

## find out datatype referred to in "unable to store ...

This is an error message when using printlevel with the RKF45 solver Many thanks

## plot an array...

Hi, i'm a french student, i hope a little help. (sorry for my english) How can i make a 3d graph of an array with 2 variables ? I have try plot3d: `plot3d(array[x,y], x=1..10, y=1..10);` and then: Warning, unable to evaluate the function to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct. In the help, it is said that plot works only with functions. Maybe i have to built a function with the array... I don't know in fact! Thanks for your help

## How to obtain the coefficents of variable???(Basic...

>alias(phi=phi(x)): > U := u(x)*phi^(j-2): > cc := expand(6*U*(diff(U, x))): > select(has, cc, 1/phi^5); # can obtain > coeff(cc,phi^(2*j-5)); # obtain 0 0 > select(has, cc, phi^(2*j-5)); # obtian 0 0 I want to obtain the coefficents of variable,phi^(2*j-5), but both "coeff" and "selcet" are invaild. How to obtain the coefficents?? Many thanks in advance!

## Need some help in Non-Linear differntial equations...

Hi.... I am facing some problem in solving a Non-linear differential equation using Maple 11. So many times maple 11 doesnot execute the command and comes out. Sometimes, it just says evaluating for a long time and nothing happens. I would be very happy if you can give me the solution of the same with an example. Regards Sripad

## Storing and using imtermediate results...

With my calculator, I can store and then use intermediate results in the following way. Lets say the result of an equation is 1.234 and I will be using those results in other calculations. If I enter 1.234->a where the arrow represents the store key, the value of 1.234 in now stored as "a" and I can use "a" in further calculations, for example 2a followed by enter will return 2.468. How do I do the same type of thing with maple? (Thank you)

## Expand and Collect commands...

With my graphing calculator (TI-voyage200) I can expand and collect multiple angles per the familiar trig foumulas. For example with my calculator I can enter tExpand(sin(2*x)) and 2*sin(x)*cos(x) is returned. To do the reverse I simply enter tCollect(2*sin(x)*cos(x)) and sin(2*x) is returned by my calculator. With Maple, I find that I can use expand(sin(2*x)) to get 2*sin(x)*cos(x) but collect(2*sin(x)*cos(x)) doesn't perform the reverse the operaton. How can I do the reverse operation, for instance by entering what command along with 2*sin(x)*cos(x) and have sin(2*x) returned???

## Matrix from the section of rows and columns of ano...

Hello everyone,I'd like to ask a question. Using the "LinearAlgebra" package, is there a (automatic) way to create a matrix from the section of rows and columns of another matrix already in use? That is, we have A:= a 5X4 matrix and we want to create, let's say a 3X2 matrix from the elements of A that belong in the section of rows 2,4 and 5 and columns 2 and 4 of A. Ok, we can write a small routine, but I would like to know if there's a fast and straight way to do that. Thanks in advance!