## surd produces absurd result...

I am trying to solve an equation using surd and I get a strange result.

solve(surd(x^4,8)=-2)
4, -4, 4 I, -4 I

These solutions are clearly wrong.

The equation (x^4)^(1/8) = -2 has no solution.

This problem is equivalent to asking the computer to solve sqrt(x) = -2

which has no solution in R or C.

However if I type

solve((x^4)^(1/8) = -2) , then I get no answer, which is what I expected.

Why does surd behave in this unexpected way.

Also another thing I am wondering, why doesn't Maple simplify (x^4)^(1/8) to x^(1/2).

I tried the simplify command it didn't work.

## bizarre bug in Physics tensor manipulation...

Here's a short tensor manipulation which goes totally bananas. Basically I have a metric, and I define a vector k, and right at the end I calcualte the covariant derivative of it. In the metric and elsewhere I have a constant epsilon, a function of time a(t), and 2 functions of all coords, Phi and psi. Then at the end it gives the covariant derivative of k, but now with epsilon and a as functions of all coordinates.

Any idea what's going on??

code:

restart;
with(Physics);with(PDEtools):
Setup(coordinatesystems=spherical);

ds2:=expand(a(t)^2*(-(1+2*epsilon*Phi(r,theta,phi,t))*dt^2+(1-2*epsilon*psi(r,theta,phi,t))*(dr^2+r^2*dtheta^2+r^2*sin(theta)^2*dphi^2)));
declare(%,(H)(t),(k0,k1,k2,k3)(X));
Setup(metric = ds2);

Define(k[~mu]=[-1/a(t)^2+epsilon*k1(X),epsilon*k2(X),epsilon*k3(X),1/a(t)^2+epsilon*k0(X)]);

Define(NullGDE[nu]=(k[~mu](X)*D_[mu](k[nu](X))),OpticalDeformationMatrix[mu,nu]=(D_[mu](k[nu](X))));

(OpticalDeformationMatrix[1,1,nonzero]);

the final output is Matrix(1, 1, [[(-(2*((diff(epsilon(X), r))*(psi(X))(X))+2*epsilon(X)*(diff((psi(X))(X), r)))*(epsilon(X)*(k1(X))(X)*((a(t))(X)^2)-1)*a(t)-(2*epsilon(X)*(psi(X))(X)-1)*((diff(epsilon(X), r))*(k1(X))(X)*((a(t))(X)^2)+epsilon(X)*((diff((k1(X))(X), r))*((a(t))(X)^2))+2*epsilon(X)*(k1(X))(X)*(a(t))(X)*(diff((a(t))(X), r)))*a(t)+epsilon*psi[r]*(epsilon*k1(X)*(a(t)^2)-1)*a(t)-epsilon^2*psi[theta]*(a(t)^3)*k2(X)-epsilon^2*psi[phi]*(a(t)^3)*k3(X)-(2*(diff(a(t), t))*psi(X)*epsilon+psi[t]*a(t)*epsilon-(diff(a(t), t)))*(epsilon*k0(X)*(a(t)^2)+1))*(1/a(t))]])

where epsilon is now a function!

## Where can I find extensive examples of dsolve,nume...

The help text for dsolve,numeric,events describes many kinds of triggers and actions and other event specifications, but shows only a very limited selection of examples of these possibilities.

Please tell me of any sources containing extensive examples of the wide variety of available specifications and the problems they are useful in solving.

## How to read this Maple code from help on Maple web...

I was learning about Maple, but I do not understand this code below. This does not look correct.

When I type it on my worksheet, I get these errors

Sometimes I wonder if any one at Maplesoft actually looks at their own help web pages and try to use them, or is just the poor users who do that.

## what is special about variable y and z? ordering o...

I noticed Maple gives different order of term (but still correct) when variable y or z is used, vs. other letters in this computation.

In this example below, integral results are given, using one letter of the alphabet at a time in the integrand.

Only when the variable is y or z, Maple shows expression in different form from all the others (negative sign pulled out). The result are correct ofcourse, but was wondering why this hapens only for these two variables? I would have expected that variable name (letter used) should not make any difference to the final form.

restart;
interface(rtablesize=infinity):
chars:=[seq(parse(StringTools:-Char(i)),i=97..122)]: #generate a..z variables, may be there is better way?
Matrix([seq([chars[i0],simplify(int((c0^2 - c1^2)/(chars[i0] - x0+I*c3), x0))],i0=1..nops(chars))]);

Gives (this below. Notice the very last 2 entries below)

Is this something common in Maple? Does it depend on the computation being performed? Can a user do something to tell Maple not to change order/form of expression depending on what variable letter is used?

hi

thanks..

dsolve.mw

## Automatically convert and paste as 2D math...

Is there a way to automatically convert and paste my clipboard contents as 2D math?

by: Maple 2016

Using a mouse's back/forward buttons or alt+ left arrow/ alt+right arrow did not work in Maple 2015 and they still don't work in Maple 2016.

Also, if you select anywhere in the search bar, it automatically selects all the words.  I sometimes (most the time) want to change only one word.

Im using x64 Windows 10 and it also did it when running Windows 8/8.1 .   Does anybody else have this problem?

Can it be fixed please if not?

## error after use ''for'' in program...

hi..when i use rule [for] in maple code i encounter error'''''

Error, (in dsolve/numeric/process_input) input system must be an ODE system, found {f1(x), f2(x), f3(x), ApproximateInt(-4*cos(theta)^2, theta = 0. .. 1, method = simpson), ApproximateInt(4*cos(theta)^2, theta = 0. .. 1, method = simpson), ApproximateInt(8*cos(theta)^2, theta = 0. .. 1, method = simpson)}''''''''

99999999999999.mw

i want for different beta for example beta=0, 40 and 80 this lines will computed three times

''with(Student[Calculus1]); a1 := ApproximateInt(g1*g1, theta = a .. 1, method = simpson); a2 := ApproximateInt(2*(g1*g1)+3*g1*(diff(g1, theta, theta)), theta = a .. 1, method = simpson).......................''

by {for i from 1 by 1 to 3 do } and final gain ''ITRA_1_W[m] := eval(fy33*g3, fixedparameter)'' that have 3 amount.

when i use  rule {for i from 1 by 1 to 3 do ...  }   integral not computed and showed for example:::

a1=ApproximateInt(4*cos(theta)^2, theta = 0. .. 1, method = simpson)!!!!!!!!

thanks..

## How do I find and access a temporary .stl file tha...

I read a posting by Mr. Stephen Forrest on Thingiverse about using the exportplot command to export a 3D plot as a .stl file. I have a 3D printer and need the convert the plot from the Maple file into an .stl file.

Here is the posting I am referencing:

Thingiverse/3dmodelimportexport.pdf

I was able to follow the commands successfully in the referenced paper for a hyperboloid or revolution that I plotted in Maple - it was very helpful. However, I could not figure out how to access the temporary .stl file that was created so that I could open it using my 3D printer's software.

My question is: Once I execute the "exportplot(stl, hyprev)" command that I inputted, how can I find the file in the Temporary Directory in order to open it from the software I use for my 3D printer?

I would appreciate any further details you can provide for accessing the temporary .stl file I created in order to be able to print the object.

Thank you!

## Make Maple touch friendly!

If you try and scroll a page up or down, it just selects the content.  How hard would it be to fix this?

## Math Input Panel...

I use Maple on a Surface Pro 4 tablet and the math input panel does not work with Maple.  This would be a great feature to have.  Or does anybody know how to get it working?

## Substituting value with template problem...

Why can't I sub both values at the same time and/or why does k stay symbolic but not d?

## Error, (in dsolve/numeric/bvp) system is singular ...

i have problem on running the ode bcs

there is cos n sine in ther ode

any idea to solve this ?

i have attched it

thnks
Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/Sc.mw .

## Why can't I assign to a name the expression A=(1,2...

Using Maple 2016, I created a new Document with one line:

A=(1,2,3)

Right-clicking on this expression I thought I could choose Assign to a Name, as is done in Clickable Calculus Series - Part 3: Multivariate Calculus, found here:

However, Assign to a Name does not appear in the context menu.

On the other hand, if I write

B=1,2,3

(with no parentheses) and right-click on this expression then Assign to a Name does appear in the context menu.

Any insights on this?

Thanks.

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