## 7 Badges

18 years, 124 days

## I have tried that, but I get error messa...

I have tried that, but I get error messages.

AB

## 2nd derivative -- 3rd remark...

I apologize that I have not made my point specifically enough.  I often use Maple as a worksheet on which I do calculations manually, using Maple only to do the tedious stuff.  So, if I have a complicated expression with lots of variables, I might copy & paste it into eval.  This doesn't work if the expression contains a 2nd derivative, expressed conventionally.

## still the 2nd derivative...

The reponse by Robert Israel does not answer my question.  Let's say I have a complicated expression with many variables, one of which is a 2nd derivative, expressed conventionally.  I know the numerical values of these variables, so I use eval to get a numerical answer for the entire expression.  If I express the second derivative in standard math notation, it will be taken as one containing an exponent.  To avoid this, I could simply rename the 2nd derivative as e.g., x.  Is there another way?  I guess not.

## How about -1...

Isn't -1 a solution?

## Request for a simpler answer...

I don't want to appear ungrateful, but I was hoping for a simpler answer.  For example,

extrema(3*x^4-4*x^3,{},x);

yields

{-1, 0}

It would be nice if this command could be modified to consider the endpoints.

## The bug...

When I referred to "the bug," I was referring to the lost files, not the crashing.  But I gather from Alec's answer that lost files is still a problem.  That's surprising since it would seem to be easy to fix; other programs don't have that problem -- e.g., WordPerfect.

Crashing is more difficult to deal with since so many different situations can cause a program to crash.  In my latest crash, I had imported a PDF file, & then I decided to delete it (or maybe I tried to put it on the clipboard -- I forget which), & Maple crashed.

Alla

## PDEtools error...

Sorry to take so long to continue this thread.  The first command is OK but the second

PDEtools:-declare(u(x));

gives the error message

'PDEtools' does not evaluate to a module.

How to fix this?

Alla

## Kokovidis' solution doesn't work for me...

Kokovidis' solution doesn't work for me.  I am using Windows XP, Maple 9.5, classic interface, & I don't have a red maple leaf or filtered HTML as option on the Export menu.  Is there something that will work for this configuration?

Alla

## Reply to Israel...

Answer to your question re Maple's habit of converting even simple decimals to scientific notation while user is inserting standard nonexecutable math into a text region:

Version 9.5
Classic
Windows XP
Worksheet
Insertion via keyboard

Alla

## Problem reduced to essentials...

Thanks to Acer for his explanation.  So it appears that the solution can be reduced to two steps:

factor(a^3 - 1);

subs(a = x^(1/3), %);

Alla

## need natural language translation...

Jakubi's code for factoring (x - 1) as the difference of two cubes works fine, but I am having trouble understanding the Maple code.  Could someone please give me a natural language translation, symbol by symbol?

The code is

```subs(a=x^(1/3),(factor@subs)(x=a^3,x-1));
(1/3)        (2/3)    (1/3)
(x      - 1) (x      + x      + 1)

```

Many thanks.

Alla

## Here are the factors:...

Here are the factors I'm looking for:

(x - 1) =  (x^(1/3) - 1)  (x^(2/3) + x^(1/3) + 1)

Alla

## Dirichlet function -- modified version...

Here is a modifed version, said to be graphable:

f(x) =  {  0,     for x irrational
{  1/b,  for x = a/b a reduced fraction

Alla

## RealDomain or not...

I first tried limit without RealDomain & got the wrong answer.  Since using RealDomain had cured other problems in this thread, I decided to try it, but got the same wrong answer.  The real question is: How can I get the right answer?

Alla

## Why doesn't limit work here?...

Why doesn't this work?

> use RealDomain in

f39 := x -> 4*x^(2/5)-2*x;

limit(f39(x),x=0,real);

end use;

>

I'm getting zero, but answer should be "undefined," no?

Alla

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