nm

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MaplePrimes Activity


These are questions asked by nm

What is the logic behind this?

expr:=(c[2]+x)^3;
simplify(expr)

Which is what expected. But 

expr:=(c[2]+x)^3+a;
simplify(expr)

gives

Which does not look simpler to me. I expected it to be the same as before but with "a" added.  This is what Mathematica gives for comparison

I know I can use simplify with size option. But my question is, how did Maple decide that x^3 + 3*x^2*c[2] + 3*x*c[2]^2 + c[2]^3 + a is "simpler" than (c[2] + x)^3 + a ? It must use some logic which I am trying to understand.

Maple 2022.2 on windows 10

I've probably asked about this long time ago but I do not remember now. But it is still a problem any way in 2022.2

Compare these two results

code is

 

restart;

alias(seq(c[k] = _C||k, k = 0..10));
c[1]*h(x);
Int(c[1]*h(x),x);


restart;
c[1]*h(x);
Int(c[1]*h(x),x);

I tried with typesetting level as extended and standard and same result.

Is this a know issue? It is not a big deal as it only affects display but it will be nice to find why it happens when using alias.

 

after updating to latest Physics package, I find now latex geneated is invalid as it gives compile error.

I looked at old files I have and I see the latex generated before was correct. so something changed in the latex() command to cause this and now none of my files compile when I run my Maple program.

Before, same code used to generate this

 \left(-x^{2}+1\right) \left(y^{\prime}\right)^{2} = 1-y^{2} 

which compiled correctly.

Here is worksheet
 

interface(version)

`Standard Worksheet Interface, Maple 2022.2, Windows 10, October 23 2022 Build ID 1657361`

Physics:-Version()

`The "Physics Updates" version in the MapleCloud is 1378 and is the same as the version installed in this computer, created 2023, January 29, 12:4 hours Pacific Time.`

latex:-Settings(useimaginaryunit=i,
      usecolor = false,
      powersoftrigonometricfunctions= mixed, ## computernotation,
      leavespaceafterfunctionname = true,
      cacheresults = false,
      spaceaftersqrt = true,
      linelength=10000  
);
Typesetting:-Unsuppress('all'); #always do this.
Typesetting:-Settings(prime=x,'typesetprime'=true); #this says to use y'(x) instead of dy/dx    
Typesetting:-Suppress(y(x)); # this says to use y' and not y'(x)

[useimaginaryunit = i, usecolor = false, powersoftrigonometricfunctions = mixed, leavespaceafterfunctionname = true, cacheresults = false, spaceaftersqrt = true, linelength = 10000]

x, false

ode:=(-x^2+1)*diff(y(x),x)^2 = 1-y(x)^2;

(-x^2+1)*(diff(y(x), x))^2 = 1-y(x)^2

latex(ode)

\left(-x^{2}+1\right) y^{\prime}^{2} = 1-y^{2}

 

 

The error from the latex compiler is 

 

\documentclass[12pt]{book}
\usepackage{breqn}
\usepackage{amsmath}
\begin{document}

\begin{dmath*}
\left(-x^{2}+1\right) y^{\prime}^{2} = 1-y^{2}
\end{dmath*}

\end{document}

compiled using texlive lualatex command gives

(/usr/local/texlive/2022/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
! Double superscript.
<recently read> \mathsup 
         
l.12 \left(-x^{2}+1\right) y^{\prime}^{2}
                                        = 1-y^{2}
? 

The fix is to keep same latex as before or use an extra {} like this  {y^{\prime}}^{2} 

but I think \left(y^{\prime}\right)^{2} looks better. But y^{\prime}^{2} is definitly wrong latex.

Download latex_problem.mw

interface(version);

`Standard Worksheet Interface, Maple 2022.2, Windows 10, October 23 2022 Build ID 1657361`

restart;
ode := diff(y(x),x)/y(x)-(3*(4*x^2+y(x)^2+1))/(2*x*(4*x^2+y(x)^2-2-2*x))=0;
DEtools:-odeadvisor(ode);
sol:=dsolve(ode,y(x));

(diff(y(x), x))/y(x)-(3/2)*(4*x^2+y(x)^2+1)/(x*(4*x^2+y(x)^2-2-2*x)) = 0

[_rational]

Error, (in dsolve) invalid subscript selector

 

Download error_jan_27_2023.mw

I am a little not clear why Maple's odeadvisor gives [_2nd_order, _reducible, _mu_xy] as an ode type for a second order ode which is already exact as is.

When the ode is exact, then no integrating factor mu is needed (or rather mu=1). But Maple says the ode is "reducible" using an integrating factor mu(x,y)

restart;
ode:=x*diff(diff(y(x),x),x)+(y(x)-1)*diff(y(x),x)=0;
DEtools:-intfactor(ode);
DEtools:-odeadvisor(ode)

 

THis ode is Kamke's 6.78, it is alslo mentioned in this paper in table 1 at page 18

I am just little confused, about the terminology. I thought reducible means the ode reguire an integrating factor of the form mu(x,y) or my(x,y') or mu(y,y') when it is not exact in order to make it to an exact ode so it can be now solved.

Why would odeavisor then says an ode which is already exact is also reducible using mu(x,y)?

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