matrix_inverse.mw

Here attached is my script. The execution of the worksheet gets stuck at the MatrixInverse(M) step. What do you suggest in order to speed up the computation?

As you can see, my matrix M is a 3x3 symmetric matrix, but quite convoluted. Eventually, I need to multiply the resulting inverse by another (row) vector.

Thank you for looking into this!

I do not remember is this was asked before.

In other OOP languages such as Java, it allows one to name object variable name same as method name. I found this example on the net for java to illustrate

class Test {

  private boolean isVal;

  public boolean isVal() {
      return isVal;
  }

}

In Maple, this is not allowed. So now I have to come up with new name for either the method or the variable that returns that hidden internal variable.

Here is an example

A:=module()
  option object;
  local is_valid::truefalse:=false;
  export is_valid::static:=proc(_self,$)::truefalse;
    return _self:-is_valid;
  end proc;
end module;

THis gives error

Error, (in A) exported variable `is_valid` cannot be multiply declared

It will be nice if Maple allows this. For now one has to rename either the variable or the method. Which is little annoying.

Is this something that could  be easily added to Maple in a future release?

I changed today my code to use DEtools:-odeadvisor(ode,y(x),[linear]); to check that the ode is linear or not before calling DEtools:-convertAlg 

The problem is that sometimes the advisor returns _linear on what is not linear ode (at least the way it is originally written). Here is an example

              (x+y(x))*diff(y(x),x) = 0;

From help page:

So now I am worried  that using odeadvisor to check for linear ode is not the right method.

Is there a build-in method in Maple to check if an ode is linear or not? (I do have my own code to do this, but I thought it is better to use a buildin method, as it will be more robust).

Should DEtools:-odeadvisor(ode,y(x),[linear]) have returned _linear in this case?

Download why_fail_sept_17_2022.mw

Hi senior, I am using Maple 2022 version. I am facing a issue regrading opening of maple worksheet. If connected with wifi then maple worksheet will open and work properly, while i disconnected the internet, maple crashed and pop up a message to activate license again..

dAlmbert ode has the form

Also from Maple own help page, it agrees with Wikipedia and says:

Now, given this ode

ode:=y(x)=ln(cos(diff(y(x),x)))+diff(y(x),x)*tan(diff(y(x),x));
eval(ode,diff(y(x),x)=p)

Then clearly the above is not dAlmbert. Right? it is missing the x. But odeadvisor says it is:

restart;
ode:=y(x)=ln(cos(diff(y(x),x)))+diff(y(x),x)*tan(diff(y(x),x));
DEtools:-odeadvisor(ode)

What Am I missing here?

Update

These are the rules I know about this ode. For y=x f(p)+ g(p). 

g(p) can be zero, yes, but in this case, f(p) has to be nonlinear in p for it to be dAlembert (else it will be either separable or linear.

I did not think f(p) can be zero and it remains dAlermber, even if g(p) remains nonlinear in p. So y=g(p) can not be dAlembert, even if g(p) is nonlinear.

May be Maple uses its own definition of dAlembert?. I do not know. This will be new definition to me. Is there a reference that mentions this case of y=g(p) classified as dAlembert for nonlinear g?

Maple 2022.1 on windows 10

Download Uniformly_accelerated_motion.mw

I need to count how many times a special function shows up in an expression.

The problem is that indets returns a set. So if the same function shows up more than one time in the original expression, with same arguments, only one of these will show up in the result. So I would not know if there were mmore than one of these.

Here is a simple example, using sin(x) here.

restart;
expr:=sin(x)+3*cos(x)*sin(x)+1/sin(2*x);
indets(expr,'specfunc(anything,sin)')

#gives
#   {sin(x), sin(2*x)}

So when I do nops() on the above, it gives 2 and not 3.

How to obtain number of times a function shows in an expression, even it if is repeated?

Hi everyone, I have copied soem code from a paper. I hope to try and manupiluate some of the varables. However it seems while I am coping the code I get this error Error, (in dsolve/numeric/process_input) system must be entered as a set/list of expressions/equations .I have checked online but it seems that there is nothing I can find to fix this problem. My code is posted below 

Thanks for your time and help!

Download Test_1.mw

Hi, everyone! I am a new user to maple and I need to import some code I have found from a paper, just so I can manupluate some of the variables. However when I have copied and pasted my code, I keep getting the error Error, mismatched or missing bracket/operator.  I did check online and it seems to be a bracket missing but I have copied without errors from the source. 

I have attached a picture and did a copy paste of the code that is giving me an error below. 

Thanks for your help 

x[1] := l[1]*sin(theta(t));
y[1] := -l[1]*cos(theta(t));

x[2] := -l[2]*sin(theta(t));
y[2] := l[2]*cos(theta(t));
R[1] := vector(2, [x[1], y[1]]);
R[2] := vector(2, [x[2], y[2]]);
'R[1]'':=map(diff,R[1],t):

Download mw.mw

in a worksheet, typing

r:=(x^2 - 2*x - 1)/4;

Maple returns

But when typing

r:=(x^2 - 2*x - 1)/(4*x);

Now it does not expand terms and gives what is expected

Is there a way to make the first example remain unexpanded? Same with Mathematica:

I know this only affects the display only. But it is annoying, as I want to see the numerator and denominator on the screen as I put them there and not have them change.

I tried changing the typesetting level, but this had no effect.

I used to like Maple becuase it does not change anything unless asked to, and everything is explicit, which is better.

Now I am starting to change my mind on this aspect of Maple.

How should I handle the limit in the integration answe?. I don't see why it is necessary.

Download Q_9-9-22_limit_in_integral.mw

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.

Hi ---

      I know how to add the Angstrom symbol to a plot's axis label using my mouse and the palette menu.  How can I add the Angstroms symbol programmatically to the plot command?  Thanks!

David

Hello,

I have a nonlinear system of 12 SYMBOLIC equations in 6 variables. I am using solve() but it's taking me ages and will probably return the "Kernel connection has been lost" error after a half-day/ a day.

How do I solve it? Is it even possible to solve it? Is there a way to solve it approximately?

Thanks