## Problem with calculations on different computer...

Asked by:

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?

## problem with subs rule...

Asked by:

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;
 (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;
 (2)

 > nondimRule1:=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;
 (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);
 (5)
 > dropnRule:=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);

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

Download subs.mw

## local symbols and global symbols scope question...

Asked by:

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?

## New bug in Maple 2017 ?...

Asked by:

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?

## "Proof Assistant" in to do list of Maple developer...

Asked by:

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

## Final solution not visible...

Asked by:

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.

## If "error message" then .......

Asked by:

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

## Error, (in limit/dosubs) invalid input: `limit/dos...

Asked by:

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

## Exponential Fit Problem...

Asked by:

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

## how to reverse after expanding polynomial...

Asked by:

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?

## InhomogeneousDiophantine...

Asked by:

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?

## how to extract the data of a Maple figure to plot ...

Asked by:

dear all,

i have a Maple file where I have made some calculations solving equations, and have plotted a figure. I would like to know how to process this figure in a way so that i can get the data points of the plot, in order to plot them separately in a different software such as Excel or MATLAB for example.

Right-click on the figure and exporting doesnt help as the options are only to export the figure to pdf, bitmap, png, etc. This is not what I want. I want to get the data of the fiogure, so that i can plot in external software (excel, MATLAB etc)
can you give some suggestions as to how to do this ?
thanks in advance
best regards,

Abhishek

## how to solve this system?...

Asked by:

sys1:=-.736349402144656384 = -1.332282598*10^12*(-.99999999999999966)^po1-1.332282598*10^12*(-.99999999999999966)^po2-.735533633151605248*Resid;

sys2:=.326676717828940144 = 1.331567176*10^12*(-.99999999999999966)^po1+1.331567176*10^12*(-.99999999999999966)^po2+.325144093024965720*Resid;

sys3:=.590327283775080036 = -1.072184073*10^9*(-.99999999999999966)^po1-1.072184073*10^9*(-.99999999999999966)^po2+.589610307487437146*Resid;

Minimize(sys1, {sys2,sys3},assume = nonnegative);

complex value encountered;

## how to calculate basis for this basis...

Asked by:

how to calculate basis <1,4,0>, <1,0,4> for eigenvalue 2;

how to calculate basis <1,0,1> for eigenvalue -1;

with(LinearAlgebra):
A := Matrix([[-2,1,1],[0,2,0],[-4,1,3]]);

sys1 := Eigenvalues(A)[1]*IdentityMatrix(3)-A;

sys1 := Eigenvalues(A)[2]*IdentityMatrix(3)-A;
sys1 := Eigenvalues(A)[3]*IdentityMatrix(3)-A;

B:=[<sys1[1,1],sys1[2,1],sys1[3,1]>,<sys1[1,2],sys1[2,2],sys1[3,2]>,<sys1[1,3],sys1[2,3],sys1[3,3]>,<0,0,0>];
LinearAlgebra:-Basis(B);

but not <1,4,0>, <1,0,4> for eigenvalue 2

## integrals, series and products...

Asked by:

A few days ago I was browsing through some books in my collection, that by Gradshteyn and Ryzhik in particular. What fraction of the intregrals, series and products therein can Maple handle correctly?  Besides special functions these properties are valuable components of symbolic mathematical software.  If the answer to this question is not nearly everything in that printed compilation, this inclusion in Maple is a worthy objective.

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