## Alec Mihailovs

Dr. Aleksandrs Mihailovs

## 4470 Reputation

20 years, 25 days
Mihailovs, Inc.
Owner, President, and CEO
Tyngsboro, Massachusetts, United States

## Social Networks and Content at Maplesoft.com

I received my Ph.D. from the University of Pennsylvania in 1998 and I have been teaching since then at SUNY Oneonta for 1 year, at Shepherd University for 5 years, at Tennessee Tech for 2 years, at Lane College for 1 year, and this year I taught at the University of Massachusetts Lowell. My research interests include Representation Theory and Combinatorics.

## isolve with inequalities...

I understand that isolve doesn't work with inequalities, at least it is not mentioned on the isolve help page. Still, the following seems strange,

```isolve({40*a+60*b<=150, a>=0, b>=0});

{b = _NN1~}
```

It is related to that post.

Alec

PS By the way, some of such problems that Maple can't solve, are not even high school problems - they are an elementary school (and maybe even kindergarten) problems. -Alec

## Eval help page...

Eval help page contains the following statement:

Since eval does pointwise evaluation, eval cannot be used to evaluate an expression at a singularity. Use limit instead.

This is a serious error showing that the person writing it doesn't understand the difference between the value of a function at a point and the limit at that point.

At discontinuity, the value of a function is _not_ equal to the limit - that's why it is discontinuity. If the value of a function was equal to the limit, the function would be continuous at that point.

An example:

## Export to wmf...

I just tried to export the following plot (from a Student forum topic) to wmf (Windows Metafile) in Standard Maple,

```with(plots):
a := plot((x^2-2)/(x-sqrt(2))):
b := pointplot([sqrt(2), 2*sqrt(2)+0.05],
symbolsize = 15, symbol = circle, color = blue):
c := pointplot([sqrt(2), 2*sqrt(2)+0.05],
symbolsize = 10, symbol = solidcircle, color = white):
display(a, b, c);
```

It has a black background! Also, the picture is smaller size, 256x256 instead of 400x400.

Other problems - copying from Standard Maple and pasting to Notepad before copying from Notepad and pasting here, all :s were copied as ;s, and ; at the end wasn't copied at all (but it was selected.)

Also - why I had to add 0.05 in the pointplot commands - the point was located lower than it should.

Also - why I tried to export to wmf - because all other export options that I tried before that, produced low quality pictures with the point located lower than it should and with jagged lines.

Another thing - when I copied from My files and pasted here the html code for the picture, it had two </a> at the end instead of one.

Alec

## Solve inequalities...

```solve({a<=a*b,b<=1});
{a = a, b = b}
```

Alec

## workprec in fdiff...

I'm not sure, but it seems as if workprec in fdiff may have a bug. See an example. Or, maybe, something is wrong with the numerical ode solution there.

Alec

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