Unanswered Questions

This page lists MaplePrimes questions that have not yet received an answer

Is there an assumption or some other way I can tell Maple to avoid such errors when using odetest, as I get many of them.

I think the solution Maple gives is correct. But odetest generates these strange innternal error that it does not know the sign of a complex number.

restart;
ode:=x^2*diff(y(x), x$2) + (cos(x)-1)*diff(y(x), x) + exp(x)*y(x) = 0;
sol:=dsolve(ode,y(x),series):
odetest(sol,ode,series,point=0);

Error, (in odetest/series) need to determine the sign of I*3^(1/2)

I've seen such error many times before and it is still not fixed in release after release.

I am using Maple 2022.1 on windows 10.

To make the "Simple External Code Function" example of the tutorial work, an external complier is required.

in MapleSim:-CreateDataRecord) invalid input: dsolve/numeric/ToExternal:-AddTempFile expects its 1st argument, f, to be of type string, but received [[["f1", 1864151924736]]] (3.597s)

Update:

help(Setup, Compiler) in Maple 2022 provides a link to supported compilers, which are Visual Studio 2017 and 2019.

In the list of available downloads there is no mention of "Express Edition". Which of the packages can be installed alternatively?

I don't understand why the solution of sys_2 isn't those of sys_1 when M__p=1 and M__a=0 ?

Traces of the computation seem to indicate that dsolve proceeds exactly the same for sys_2 and sys_1 .

Please note that sol_1 contains a term of the form t*cos(t) that sol_2 doesn't, thus the question: "Is sol_2 correct?"

Could you help me to fix this?
TIA

restart

infolevel[dsolve] := 4;

4

(1)

sys_1 := {diff(x(t), t$2)=sin(t)-x(t), x(0)=0, D(x)(0)=0};
sol_1 := dsolve(sys_1)

{diff(diff(x(t), t), t) = sin(t)-x(t), x(0) = 0, (D(x))(0) = 0}

 

Methods for second order ODEs:
--- Trying classification methods ---
trying a quadrature
trying high order exact linear fully integrable
trying differential order: 2; linear nonhomogeneous with symmetry [0,1]
trying a double symmetry of the form [xi=0, eta=F(x)]
-> Try solving first the homogeneous part of the ODE
   checking if the LODE has constant coefficients
   <- constant coefficients successful
   -> Determining now a particular solution to the non-homogeneous ODE
      building a particular solution using variation of parameters
<- solving first the homogeneous part of the ODE successful

 

x(t) = (1/2)*sin(t)-(1/2)*cos(t)*t

(2)

sys_2 := {(M__p+M__a)*diff(x(t), t$2)=M__p*sin(t)-x(t), x(0)=0, D(x)(0)=0};
sol_2 := dsolve(sys_2)

{(M__p+M__a)*(diff(diff(x(t), t), t)) = M__p*sin(t)-x(t), x(0) = 0, (D(x))(0) = 0}

 

Methods for second order ODEs:
--- Trying classification methods ---
trying a quadrature
trying high order exact linear fully integrable
trying differential order: 2; linear nonhomogeneous with symmetry [0,1]
trying a double symmetry of the form [xi=0, eta=F(x)]
-> Try solving first the homogeneous part of the ODE
   checking if the LODE has constant coefficients
   <- constant coefficients successful
   -> Determining now a particular solution to the non-homogeneous ODE
      building a particular solution using variation of parameters
<- solving first the homogeneous part of the ODE successful

 

x(t) = sin(t/(M__p+M__a)^(1/2))*M__p*(M__p+M__a)^(1/2)/(M__p+M__a-1)-M__p*sin(t)/(M__p+M__a-1)

(3)

eval(sol_2, [M__p=1, M__a=0])

Error, numeric exception: division by zero

 

 

Download SomethingWrong.mw

PS: Already, in the following case, dsolve doesn't return the solution of sys_1.

sys_3 := {(A+B)*diff(x(t), t$2)=(A+B)*sin(t)-x(t), x(0)=0, D(x)(0)=0};
sol_3 := dsolve(sys_3)

If I do this

sys_4 := {(A+B)*diff(v(t), t)=(A+B)*sin(t)-x(t), diff(x(t), t)=v(t), x(0)=0, v(0)=0}:
sol_4 := dsolve(sys_4)

I get a very complex solution wich contains a piecewise function which separates the cases A+B=1 and A+B<>1.
Evaluating sol_4 for A+B=1 gives the same expression than sys_1:

simplify(eval(sol_4, A=1-B), trig)
       /       1                  1          1         \ 
      { v(t) = - sin(t) t, x(t) = - sin(t) - - cos(t) t }
       \       2                  2          2         / 

Here is a workaround to get the correct solution of sys_2:

sys_5 := {(M__P+M__A)*diff(v(t), t)=(M__P+C)*sin(t)-x(t), diff(x(t), t)=v(t), x(0)=0, v(0)=0}:
sol_5 := dsolve(sys_5):
simplify(eval(sol_5, [M__P=1, M__A=0, C=0]), trig)
       /       1                  1          1         \ 
      { v(t) = - sin(t) t, x(t) = - sin(t) - - cos(t) t }
       \       2                  2          2         / 

e

Currrently maple exports it in huge fonts do the pdf is really big. I would like to make the pdf smaller by decreaseasing the font size. I cant seem to find any options for that online.

 

``

NULL

U(t, r, theta, phi) = _F1(r, theta, a^2*phi+phi*r^2-a*t)

eq1 := a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)^2*(diff(U(t, r, theta, phi), t, t))-a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)*(diff(U(t, r, theta, phi), theta, theta))-(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(r^2+a^2*cos(theta)^2)^2*(diff(U(t, r, theta, phi), phi, t))+a*U(t, r, theta, phi)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)*(diff(U(t, r, theta, phi), theta))^2-a*cos(theta)*sin(theta)*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(a^2*cos(theta)^2-2*a^2-r^2)*(diff(U(t, r, theta, phi), theta))-(diff(U(t, r, theta, phi), t))*((a*cos(theta)^2-a)*(diff(U(t, r, theta, phi), t))-(diff(U(t, r, theta, phi), phi)))*U(t, r, theta, phi)*(r^2+a^2*cos(theta)^2)^2

a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)^2*(diff(diff(U(t, r, theta, phi), t), t))-a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)*(diff(diff(U(t, r, theta, phi), theta), theta))-(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(r^2+a^2*cos(theta)^2)^2*(diff(diff(U(t, r, theta, phi), phi), t))+a*U(t, r, theta, phi)*(cos(theta)-1)*(cos(theta)+1)*(r^2+a^2*cos(theta)^2)*(diff(U(t, r, theta, phi), theta))^2-a*cos(theta)*sin(theta)*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(a^2*cos(theta)^2-2*a^2-r^2)*(diff(U(t, r, theta, phi), theta))-(diff(U(t, r, theta, phi), t))*((a*cos(theta)^2-a)*(diff(U(t, r, theta, phi), t))-(diff(U(t, r, theta, phi), phi)))*U(t, r, theta, phi)*(r^2+a^2*cos(theta)^2)^2

(1)

eq2 := -a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(diff(U(t, r, theta, phi), r, t))+(U(t, r, theta, phi)^2-1)*(diff(U(t, r, theta, phi), phi, r))+(diff(U(t, r, theta, phi), r))*((a*cos(theta)^2-a)*(diff(U(t, r, theta, phi), t))-(diff(U(t, r, theta, phi), phi)))

-a*(U(t, r, theta, phi)-1)*(U(t, r, theta, phi)+1)*(cos(theta)-1)*(cos(theta)+1)*(diff(diff(U(t, r, theta, phi), r), t))+(U(t, r, theta, phi)^2-1)*(diff(diff(U(t, r, theta, phi), phi), r))+(diff(U(t, r, theta, phi), r))*((a*cos(theta)^2-a)*(diff(U(t, r, theta, phi), t))-(diff(U(t, r, theta, phi), phi)))

(2)

NULL

Download probfile.mw

I need to solve a system of coupled partial differential equations. I would like to search for a function of 4 variables but such that two of the variables only appear in a particular combination.

F(theta,r, phi*(a^2+r^2)-at).

Is there a way to enforce this?

every time we past with windows button + v

it has the form of one liner math input i want to force all pasting to have normal math input !

example

i copy two items and past them (the last one with the windows button)

   a/b,  and x/y

and i get

x/y and a/b

or another example

i want to have a script that ones ran, makes all pasting that contains one liner into normal math

this is not a scrip we need to run at the end or periodically but a package ones loaded changes the way it pastes with the windows button (something like for every past "check IF it is a oneliner IF True, then make it into normal math, else stop)

or change a setting in maple via " := " that forces all math inputs to only be able to exist in normal math, ie. disable one liner math input.

the reason i know this is a setting problem and can be fixed (easily) is this

when we look at the clipboard folder both of them are actually formed by one liner math input. and only the older copyed item has the wrong form when pasting. just take a look at the clipboard folder

when i just use CTRL + V i get the first one (with the correct form), when i use windows button + v and select the second one (i get the second one but in the wrong form)

they dont look the samme (not the letters inside but the form)

so pls help this is a major problem in order to work effectively.

Given a graph G say and a positive integer k

I am in look out how to remove

 edge-disjoint copies of G in G^k

That is edge disjoint copies of G into its power graph all possible ways 

Again it is the maximum number of copies I means 

Keeping this particular way can someone help kind help please

I will surely acknowledge it 

G into to GraphPower(G,k)

NULL

the quick brown fox jumps over the lazy dog

NULL

Download the_quick_brown_fox_jumps_over_the_lazy_dog.mw

Problem 1)   Give graph G1 and a graph G2  the problem is to extract maximum isomorphic copies of G1 from G2 such that it has no edge intersection maximum number is floor((number of edges of G2)/(number of edges of G1)) and display the Edge sets of those isomorphic graphs and the graph formed by the remaining edges sometimes their may be no remaing edges too.  Need all possible such copies.

Problem 2) Give graph G1 and a graph G2  the problem is to extract maximum isomorphic copies of G1 from G2 such that each copy has  exactly one edge intersection with each of the copies and that one edge intersection occurs only between those two copies and  display the Edge sets of those isomorphic graphs . Need all possible such copies.

If any more examples or explation will give kind help please I can give more examples or more kind please help.

I had written this c++ code years back for problem 2 which i have forgotten kind help if possible to make it better with maplesoft.

Please take your time. Kind help help plese it will be very helpful it is of real help.

orthogonal.txt

I had written this c++ code years back for problem 1 which i have forgotten kind help if possible to make it better with maplesoft.

Please take your time. Kind help help plese it will be very helpful it is of real help.

decom.txt

Need to maintain memory space as graph size is a little big may be 

would usage of database or any other be useful dont know I had done those code in c++ long back which i forgotten logic too.

Please please help based on latest technology please take your time and kind help I apologize disturb you kind help.

I would surely acknowledge for this great work as much as I can much more than I can acknowlege too

I am using Maple 2020

Consider the following code:

van_der_Waals := (p + a / V[m]^2) * (V[m] - b) = R * T:
expand(van_der_Waals);

The objective of the exercise is express the equation in a cubic form. Obvious solution is to take the output of the code above and multiplie both sides by V[m]^2. However, I would like to know if there exists a different aproach to get the same result.

simplify is a procedure in Maple that have as parameter an assumption ¿Have the assumption a default value? For example, if we consider the following code:

restart;
f:= (x^3 - 27) / (x^2 - 3 * x):
print(f = simplify(f));

The output of that code assume that denominator is not zero, so I think the procedure have a default value for assume parameter.

eval.mw This is the maple worksheet The regions are u<=-1, -1<=u<=1,u>=1

Good day everyone,

Please, I need help on how to optimize the function above. I actually wanted to plot the function with respect to "eta", but, I need the optimum value(s) for "alpha". Anyone with useful information should please help.

Thanking you in anticipation for your help.                                                             f=((-0.111000111e-1*alpha^4+.109890109900000*alpha^3+0.110726700000000e-1*alpha^2+0.133899904900000e-3*alpha+0.136700000000000e-4)*exp(-alpha*eta)+(-0.683733733e-5+0.683733733e-5*alpha^2-0.676896396e-4*alpha)*exp(-2*alpha*eta)+0.111000111e-1*alpha^4-.109890109900000*alpha^3-0.110794990900000e-1*alpha^2-0.663221721200000e-4*alpha-0.683733733200000e-5)/(.1*alpha^5-.99*alpha^4-.1*alpha^3)

About a half hour ago, there was a Post titled "Read binary file" from a new user. I converted it to a Question. Now that I want to Answer the Question, I can't find it. If you are the author of that Question, and you still want an answer, please post it again, but put it in the Questions area.

(I think that there may be a bug in MaplePrimes that makes this happen. I've had it happen several times before.)

Anyway, please respond to this regardless of what you want regarding the Question. That'll help me figure out what went wrong.

When trying to construct objects like SU(3)xSU(2)xU(1), one needs parameters to satisfy SU(n,q)xSU(n,q)xU(n,q).  What are the values of 'q' for these group constructions using the group theory package?  

thanks

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