MaplePrimes Questions

the Initial value problem is well defined but i could not find solution of the problem. A number of method have been used but all are useless. How to obtained graph of the all equations. Also can we find the value of R (radius) where P is zero.coupled_IVP.mw

We know it's true that the Inverse Laplace Transform of two functions' multiplication is the convolution of every function's Inverse Laplace Transform. I think the case can be upgraded to multiple functions, i.e.

L^(-1)(f[1]*f[2]***f[n])=L^(-1)(f[1])∗L^(-1)(f[2])∗∗∗L^(-1)(f[n])

 

 

Does Maple have build-in function, which when given an expression that depends on x and y, will separate it to a product of two functions, one that depedns on x only and the other that depends on y only?

The input mathematical expression is known to be seperable.

For example, If the input is

((3*y + y^2)*3*x)/(x + sin(x))

Then I'd the Maple function to take the above and return list or set of two parts  {(3*y + y^2)   ,     3*x/(x + sin(x) } (if it can't separate it, it can return null).

The API can be something as  

 f,g = find_product_functions(expression,[x,y])

Something like this is used on determining for example if RHS of first order ODE is separable in order to solve it more easily.  collect() does not really work for this. So Maple allready does this internally in its ODE solver when it checks if ODE is separable or not. But is the function available for users?

 

How can I to build a Spinor with Physics package? I would like to explore a sigma model  from Lagrangian density. The ideia is search the Euler-Lagrange's equation and energy density of this model.  

Hello!
I have a problem with calculations. I have a worksheet and it calculated on some computer but on another i have an error after each equation. I dont have any idea why. When i click on error i see "Sorry, we do not have specific information about your error. " What can i doo with this?

subs.mw

hi...i have a problem with subs rule

please help me.

thanks

eq81a:=m*diff(w(x,t),t$2)+c*diff(w(x,t),t)+E*Is*diff(w(x,t),x$4)+(P-f[p]*cos(Omega*t)-E*A/(2*l)*int(diff(w(x,t),x)^2,x=0..l))*diff(w(x,t),x$2)=0;

m*(diff(diff(w(x, t), t), t))+c*(diff(w(x, t), t))+E*Is*(diff(diff(diff(diff(w(x, t), x), x), x), x))+(P-f[p]*cos(Omega*t)-(1/2)*E*A*(int((diff(w(x, t), x))^2, x = 0 .. l))/l)*(diff(diff(w(x, t), x), x)) = 0

(1)

 

bc81a:=B[1](w(0,t))=0,B[2](w(0,t))=0,B[3](w(l,t))=0,B[4](w(l,t))=0;

B[1](w(0, t)) = 0, B[2](w(0, t)) = 0, B[3](w(l, t)) = 0, B[4](w(l, t)) = 0

(2)

 

 

nondimRule1:=w(x,t)=l*w[n](x/l,t/T);

w(x, t) = l*w[n](x/l, t/T)

(3)

nondimRule2:=x=l*x[n],t=T*t[n],Omega=Omega[n]/T,P=P[n]*E*Is/l^2,f[p]=f[n]*E*Is/l^2,c=c[n]*sqrt(E*Is*m)/l^2,A=2*alpha*Is/l^2;

x = l*x[n], t = T*t[n], Omega = Omega[n]/T, P = P[n]*E*Is/l^2, f[p] = f[n]*E*Is/l^2, c = c[n]*(E*Is*m)^(1/2)/l^2, A = 2*alpha*Is/l^2

(4)

intRule1:=Int(D[1](w[n])(x[n],t[n])^2,l*x[n]=0..l)=l*int(D[1](w[n])(x[n],t[n])^2,x[n]=0..1);

Int((D[1](w[n]))(x[n], t[n])^2, l*x[n] = 0 .. l) = l*(int((D[1](w[n]))(x[n], t[n])^2, x[n] = 0 .. 1))

(5)

dropnRule:=w[n]=w,x[n]=x,t[n]=t,c[n]=c,P[n]=P,f[n]=f,Omega[n]=Omega;

w[n] = w, x[n] = x, t[n] = t, c[n] = c, P[n] = P, f[n] = f, Omega[n] = Omega

(6)

 

eq81b:=convert(expand(l^3/(E*Is)*subs(int=Int,nondimRule2,intRule1,dropnRule,value(subs(nondimRule1,eq81a)))),diff);

Error, invalid input: diff received T*t, which is not valid for its 2nd argument

 

 

``

TRule;=solve(coeff(lhs(eq81b),diff(w(x,t),t$2))=1,{T})[1];

TRule

 

Error, `=` unexpected

 

``


 

Download subs.mw

 

 

One of the things I like in Maple is that I can return a local symbol from a proc() in some expression and it will not "conflict" with same symbol in the global space and will show the same.

I just do not know how Maple manages to do this.

For example:

foo:=proc(n)
   local x;
   x^n;
end proc;

And now if I do

x:=99;
foo(3);

Will return  x^3. This is even thought I had defined x:=99; before the call.

So there is one global `x` with value 99 and the `x` in the expression returned `x^3` did not get confused with the global `x`. Yet they look the same.

How does Maple manages to do this? In Mathematica, it always return local symbols with $nnn assigned to them to distinguish them from global symbols. (attaches the Module ID). For example, in Mathematica the same example above gives

Notice that the `x` returned from a proc() look different from inside the Module. It is not the same as the x in the global space.

Maple seems to be able to do the same thing, but using the same looking symbol. So it must be keeping track of things internally? It must know that the x in x^3 is not the same x in the x:=99 ofcourse.

Any idea how Maple does this?

 

With Maple 2017,when the following codes are being executed in the document mode, the error information

"Error, attempting to assign to `RealDomain:-`^`` which is protected"

will be displayed and echoed for several times, which won't appear in the previous versions of Maple.

 

 

///////////////////////////////////

 

restart

with(RealDomain):

with(Grid):

a := 1:

Seq(1/a, i = 1 .. 2)

 

///////////////////////////////////

 

 

Is this a new bug in Maple 2017?

salute ! all Maplesoft managers and employee programers ...

Is there any fortune in near future to have some kind of machin based "Proof Assistant" as built in part of Maple IDE ?

it can be better than COQ ?


also there is a great lack of user interactivity by Geometry and Geometry3d packages of maple !!!

for example most of the time it is nessesary (and more facilated) to define geometrical primitive shapes manually or making simple transformations and dissectings attaching ... rather than doing them programaticaly or by commands ?

even having traditional tools like compass ruler ... in pallettes of Geometry window ?


BEST WISHES FOR MAPLESOFT

 

 

I'm trying to solve Laplace's equation in Maple in 2-D domain. But while writing the last line "pdsolve(pdef)" (to get the final solution) and after that hitting enter, it doesn't shows anything. Please help me regaring this.

Hi!
I have the following code:

f:=proc(x)
   local u;
   Digits:=15;
   if x>10^9 
    then 
        u:=1/x; evalf(2/Pi*arccos((u*u-1)/(1+u*u)));
    else
        evalf(2/Pi*arccos((1-x*x)/(1+x*x)))
    end if
end proc;

 

The advantage is that f(+infinity) is defined in this case whereas evalf(2/Pi*arccos((1-x*x)/(1+x*x))) is not for x:=+infinity. But, I would like to extend this procedure in such a way that f(1/0) or f(something) where something is infinity or a division by zero is defined and gives the same result as f(+infinity).

I added before the preocedure f above the following code:
 

NumericEventHandler( division_by_zero = proc() +infinity; end proc ):

But, it defines a global environment. I would like a local modification of the environment only inside the procedure for f.

How to solve this issue?

Best regards,

 

Jaqr


 

f := -ln(-1-ln(exp(x)))+ln(-ln(exp(x)))-Ei(1, -1-ln(exp(x)))+Ei(1, -ln(exp(x)))
solve(limit(diff((subs(x=q, f)-f),h), h=0) = f, q);
limit(diff((subs(x=x*h, f)-f),h), h=0);
Error, (in limit/dosubs) invalid input: `limit/dosubs` uses a 3rd argument, newx, which is missing

guess an operator called Lee, Lee(f, x) = f

solve(limit(diff((subs(x=q, f)-f),h), h=0) = f, q);

suspect q = x*h or q=x*f

limit(diff((subs(x=x*h, f)-f),h), h=0);
Error, (in limit/dosubs) invalid input: `limit/dosubs` uses a 3rd argument, newx, which is missing
 
limit(diff((subs(x=f*h, f)-f),h), h=0);
Error, (in depends/internal) invalid input: `depends/internal` uses a 2nd argument, x, which is missing

See WA30 attached.  Why the error?  The variable that represents the vector is in vector form.  If I need to change this to THAXexa := ([1988.0, 1989.0, 1990.0 , ... etc], datatype=float, is there an easy way to convert the THAXexa matrix?

Thanks, Les  WA30.mw

suppose I have

g := (x-4)^2+(y-6)^2-144:

e:=expand(g)

                     e := x^2+y^2-8*x-12*y-92

How do I get from the equation of e back to g?

                         

I have troubles with the command in the title.

When I type

InhomogeneousDiophantine([[5^.3,1.3^.5,3^.5],[1.4^.2,4^.2,3^.33]],[5^.2,2^.5],[10^(-3),10^(-3)]);

I get the following

Error, (in IntegerRelations:-LLL) must have a non-negative size in each dimension

What have I done wrong?


 

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