## How to simplify this solution?...

```restart;
sol:=dsolve(diff(y(x),x)= x/(sqrt(x^2-16))*1/(2*y(x)),y(x));
```

Gives

But the solution can also be written as

I just do not know how to transform the first solution to the second simpler one. I tried:

```sol:=map(x->rhs(x),[sol]);
```

The simpler solution can be found as follows

```restart;
sol:=dsolve(diff(y(x),x)= x/(sqrt(x^2-16))*1/(2*y(x)),y(x),'implicit');
```

But the term in the middle above is

Therefore the solution is really

```eq:=y(x)^2-sqrt(x^2-16)-_C1 = 0;
solve(eq,y(x));```

Which gives

What command to simplify the long solution to the shorter one obtained from the implicit?

## where did the 3 come from? dsolve question....

The solution by Maple below is correct, but non-the-less, a little strange.

```restart;
dsolve(diff(y(x),x)=3*x^2*(y(x)^2+1),y(x));
```

Gives

Ofcourse 3*constant is still constant. But it is a little strange and have no reason for it to be there.  When I solve it by hand

What could made Maple put the 3 in there? Again, solution is 100% correct, but it could be simpler.

Maple 2017.1

## why this error message? Error, (in forget) lexical...

the following code results in an error message: Error, (in forget) lexically scoped parameter out of context

If I click on this error message, it brings me to a page which I visited too often.

if I uncomment the irrelevant minimize command, the error message disappears.

How can I prevent this error without giving irrelevant commands?

kind regards,

Harry Garst

## a problem in fsolve...

hello.i have a problem for solving this equation.i dont why my past post about this is deleted.!!!

thanks,,,

restart:

A1:= 27159:  n:= 0.59:  A2:= 70941:  h0:= 3e-4:
L:= 0.8:  dpx := -98100:  uc:= 0.007:  k:=2.7:

ODE:= (A3,y)->
(h0^(n+1)*L/sqrt(n)*(A1*exp(sqrt(n)*y/L)-A2*exp(-sqrt(n)*y/L))/k+dpx*y*h0^(n+1)/k+A3*(h0)^n/k)^(1/n)
;

 (1)

ODEINT:= proc(A3)
option remember;
local y;
evalf(Int(ODE(A3,y), y= 0..1, epsilon= 1e-7)) - uc
end proc:

ReINT:= proc(A3x, A3y)
Digits:= 15:
Re(ODEINT(A3x + I*A3y))
end proc:

ImINT:= subs(Re= Im, eval(ReINT)):

Digits:= 7:
a3:= fsolve([ReINT, ImINT]);

 (2)

A3:= Complex(a3[]);

 (3)

Solve as IVP:

Digits:= 15:
sol:= dsolve({diff(u(y),y) = ODE(A3,y), u(0)=0}, numeric, range=0..1,  output=listprocedure):

 >
 >

plots:-odeplot(
sol, [[y, Re(u(y))], [y, Im(u(y))]], y= 0..1,
legend= [real, imag], labels= [y, u(y)]
);

Verify that boundary condition at u(1) is satisfied:

abs(eval(u(y), sol(1)) - uc);

sol(.5);

 >

## How to plot orthogonal trajectories in differentia...

Dear sir,

I request your kind help with regard to the above cited subject.

With warm regards.

Mr.M.Anand

Associate Professor in Mathematics.

Aurora's Technological & Research Institute,

## Purchase and Reinstalling ...

To Whom It Might Concern,

I purchased Maple on Jun 5, 2017 for my Window laptop. However, my harddrive in my laptop was broken and i lost all my stuff including Maple. I am using my husband's laptop right now. How can re install Maple? I still have the transaction number (removed). Would you let me know what I can do to re-install the software? Also, my husband's laptop is a Mac.

I am looking forward to hearing from you.

Nancy Phu.

## How to make a workbook of a Package, for MapleClou...

I would like to create a Maple Workbook of my Lattice Package so I can put it on MapleCloud. I had an email exchange with Daniel Skoog from Maplesoft about this, and he even sent me an example that looked easy enough to adapt to my purposes. Alas, it does not work. Here is the code I wrote to assemble the already extant files:

restart;
# Build Lattice workbook following example from Daniel Skoog, MapleSoft:
currentdir();
"/Applications/Math_Calc/Maple 2015/Packages/Lattice/Lattice

Version 1.1.0 release files"
# We have all files already from the App Center submission, so just assemble the workbook
PackageTools:-Create("Lattice.maple",\
"MLA file"="Lattice.mla",\
"Lattice.help",\
"Source"="Lattice1.1.mpl",\
"Build procedure"="Lattice1.1.mw",\
"Manual"="The Lattice Package Users Guide.mw",\
"Release Notes"="V1.1 Release Notes.rtf");
Error, (in march) unable to attach worksheet file The Lattice Package Users Guide.mw

When I look at the created workbook (Lattice.maple), the only members included are Lattice.help, the Build procedure Lattice1.1.mw and the source file Lattice.mpl. In particular, Lattice.mla is not there, which is the most important one.

What am I doing wrong? What does "march" (which sounds like machine architecture) have to do with it??

I also don't quite know how to "install" it. I assume I just put the whole workbook into a directory accessible through libname ?

Mac Dude

PS: I could have sorted this privately with Daniel, but this may be of interest to others as well so I hope he'll answer through this forum.

Lattice1.1_workbook_maker.mw

## how to check for fopen() status?...

Maple help pages are terrible.  Sorry, but this is true.

I am looking for one example of how one is supposed to open a file and correctly check that the open was successful and no error occured, all done in code. As in a script.

All what help in fopen says is that if this and that, it generates an error.

"

OK. But to check for this in code? Why not show an example? the help page on iostatus just lists possible errors. Again, not a SINGLE example of actual Maple code showing how to actually check or handle an error. It just says to call iostatus() and shows the output without an example of what to do next and what to check for.

Lets say one does this:

fileName := "C:\\foo.txt";
fd       := fopen(fileName,WRITE):

Now what? How to check the above was successful? Do I need a trap and catch? catch what? Do I need to check for fd being greater or equal to zero and also use trap in addition? And if an error happens, how to know what it is? How to to format the message, etc.. all in CODE (not interactive) and not by saying just look at the screen and see if there is an error message.

Spend 30 minutes in the help pages and could not find ONE example that shows how to actually check for errors.

I have no idea who writes Maple helps pages, but I find the help pages useless most of the time.

Compare the help for linux fopen for example, where is gives exact details of how to handle the error and find the exact error, all in code.

## why dsolve solution sometimes shows as implicit wh...

Sometimes dsolve returns solution as implicit, even when not using the `implicit` option. For example

```restart;
ode:=diff(y(x),x)=(x*y(x))^(1/2):
sol:=dsolve(ode,y(x));```

Gives

Which is the same result if I had used 'implicit'.

Is there a way to tell dsolve not to do this? is it becuase it can't solve for y(x) from the above?

Maple 2017.1

## fsolve dont solve correctly ...

when i want to get awenser i have to solve it for 36 equation and 36 variabales
but maple will not give me a solution (just toss me back my variabales ) i dont know whats wrong
it will give me an awenser for lower like 20equ and 20var ?
parameters :

there is m for power an equation (equation^m) its between 2 , 2.5 , 3 , 4
and N give 2N+2var and 2N+2equ
its a hard calculation i copy it here hope u get it

h= "a number "

p := proc (x) c[-N-1]*x^2+1 end proc

dp := diff(p(x), x)

ddp := diff(p(x), x, x)

DELTA2 := piecewise(k <> j, -2*(-1)^(j-k)/(j-k)^2, k = j, -(1/3)*Pi^2)/h^2

DELTA1 := piecewise(k <> j, (-1)^(j-k)/(j-k), k = j, 0)/h

DELTA0 := piecewise(k <> j, 0, k = j, 1)

PHI := proc (x) ln(sinh(x)) end proc

dPHI := diff(PHI(x), x)

ddPHI := diff(PHI(x), x, x)

for i from -N-1 to N do x[i] := ln(exp(i*h)+(exp(2*i*h)+1)^(1/2)) end do

variabales : c[-N-1],c[-N],c[-N+1]...c[N-1],c[N] total 2N+2 var

My equations

POL := seq(simplify(eval(sum(c[k]*((eval(2*dPHI*DELTA1), x = x[j])+eval(x[j]*ddPHI*DELTA1, x = x[j])+x[j]*(eval(dPHI^2, x = x[j]))*DELTA2), k = -N .. N)+eval(ddp, x = x[j])+2*(sum(c[k]*(eval(x[j]*dPHI*DELTA1, x = x[j])+DELTA0), k = -N .. N)+eval(dp, x = x[j]))/x[j]+(c[j]*x[j]+p(x[j]))^m, x = x[j])), j = -N-1 .. N)

solving

K := fsolve({seq(POL[v] = 0, v = 1 .. 2*N+2)})

it can calculate for m=2.5 , N=15 , h=0.29669

if you can calculate it for m=3 , N=17 , h=0.41600

## Maple to accept incoming connections...

Everytime I start Maple 2017 I get a window asking me to accept incoming connection even though I did not put any restriction in System Preferences-Security-Firewall.

Is it normal?

Thank you

## "unable to store %1 when datatype=%2", -9.65986559...

hello...how i can remove this error?

thanks

 (1)

 (2)

## how can i delete of zeros in my solution in maple...

in my solution is 0.0000 . how can show it 0 and how can i show the solutions for example 10^-30 to zero(round to zero)

1.mw

## How to specify plot range via value?...

I want to plot a function f(x,y)=x^3-2x^2y. But I only want to plot values where \$x^2+y^2 <= 1\$. So far I specified the plotting range in the standard way, but I really need to specify it like I described. I want to use plot3d.

## how I can pdsolve three equations...

hello...how I can pdsolve three equations with related boundary conditions?

thanks...

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