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

Hi all,

I'm trying to solve linear programs on Maple 11, but it is not giving me an answer. Have I made a mistake? The comand I used is:

with(Optimization):

LPSolve(40*a + 60*b, {40*a + 60*b <= 150}, assume=nonnegint, maximize)

and maple returns:

"Warning, problem appears to be unbounded".

But in Maple 10, this same comand works perfect. Does someone know why Maple 11 doesn't??

Mario

I was working on this fairly short equation. The solution gives different results in Maple 11.01 and 11.02:

> solve(0.981747e-8*RR+0.16549e-34*(1/RR^3-1/(0.50e-9+RR)^3)+(0.44e-26*(1+0.127324e10*RR))*10.000^2/RR^2 = 0., RR)

The equation has 7 solutions, of which 3 are real, one of which is for example -9.959429517E-10. The correct value is negative, however Maple 11.01 (build 296069) gives 9.959429517E-10, while Maple 11.02 gives -9.959429517E-10.

I know that a computer can't generate a random number in the true sense of the word random. But I was expecting more when I went to do a rand(1..100); 5000 times and found most of the generated values to be between 1 and 10. Go ahead and give this a try:

As the discussion in this thread  did not provide me a clear understanding of the implementation and intended usage of the property 'continuous' I have looked at this subject a bit further. And as it is an underdocumented subject, it seems fit to post here some issues that I have found.

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:

Hi everyone,

I am looking at the following ODE:

x'(t) + a(t)*x(t)  - t*a(t) + b*a(t)*f(x(t)) = 0

where x is the function of t to be found
with t>=0, x(t)>0
with initial condition x(0)=x0 > 0 given
with a(t) a known function of t inside the positive quadrant, a(t)>0
with f(x) a known function of x inside the positive quadrant, f(x)>0
with b a known positive real constant, b>0

If b=0, we have a first-order linear ODE, but I'm interested in b>0.

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

My calculus book says that y = (x^2 - 2)/(x - sqrt(2)) is discontinuous at 2, but Maple finds a limit of

Does the following error message mean that the only way to remove RealDomain is to exit Maple & then start a new session?

 unwith(RealDomain):

A recent posting of Mario Lemelin showed that Maple's default numerical methods produced wrong results for a certain differential equation.  Further investigation revealed that the problem stemmed from the fact that the fourth and fifth order Runge-Kutta methods used within the rkf45 method both produce the same (exactly correct) result at any step size, causing the adaptive error analysis to go badly wrong.  This leads to the question: when do Runge-Kutta methods produce exact results for arbitrary step sizes and initial conditions?

For a partial answer, see this worksheet: View 4541_runge.mw on MapleNet or Download 4541_runge.mw

In addition to examples in that thread, here is another one,

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

Alec

Now that July has come and gone (along with most of the summer), it's time to announce the Maple Mentor Award winner for July.  Congratulations Acer...not only did you win, but you are our first repeat monthly winner!  You know the drill, so let us know what prize you would like.

Here's a limit where Maple stalls:

The best it can do is

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