## How to solve this system of equations?...

I am trying to  solve the system of equations
with(RealDomain);
solve(x^2+y^2+z^2-4*x+6*y-2*z-11 = 0, 2*x+2*y-z = -18], [x, y, z]);

I didn't get the result x = - 4/3, y = -19/3, z = 8/3.

How can I get the solution?

With Mathematica, I tried
Solve[{x^2 + y^2 + z^2 - 4*x + 6*y - 2*z - 11 == 0,
2*x + 2*y - z == -18}, {x, y, z}, Reals]

And got the correct solution.

## How do i solve and plot this PDE in maple? ...

How to plot the solution of pde

pde:=diff(u(x,t),t) =K*diff(u(x,t),x, x);

I can't step further,  i can't insert boundary value problem, plz help me to solve pde.

Hear u(x,t)->infinity  when t->infinity  and diff(u(x,t),x) =0 when x=0 for all t

## Finding average run time of a procedure...

If I have a procedure that for example produces a list of times it takes to work out the eigenvectors of a random nxn matrix from n=2..9.

Times:=[seq([n,time(LinearAlgebra[Eigenvectors](RandomMatrix(n)))],n=2..9)]:

If I want to make my data more accurate so that it works out the time it takes to find the eigenvector for each different sized matrix multiple times and then takes an average time (for each n), how would I do that?

## loops multiplying all the diagonal entries of a ma...

Hi I'm trying to make a procedure that will multiply all the diagonal entries of any random matrix together, this is what I have tried so far:

with(LinearAlgebra):
with(ListTools):
Diag := proc(A)
local aux,V,i,n;
V:=[];
n:=RowDimension(A):

for i from 1 to n do
aux := 1;
aux := aux*U2(i,i);
end do:

end proc;

but this just produces the last diagoinal entry of the matrix - how do I make the loop multiply the previous number by the next diagonal entry?

another option I've done is to make a list of the diagonal entries, but then I encounter the same problem with multiplication:

Diag:=proc(A)
local n, List;
n:=RowDimension(A);
List:=[seq(A(i,i),i=1..n)]:
end proc:

any help would be greatly appreciated!

## Converting a code into user interface clickable co...

I need to convert a maple code into a clickable user interface one. How to do it?. Thank you.

## Plot graph from array...

Hi, I've created an array from a do loop, where the number in the array is the number of degrees for which I've calculated the answer, I now wish to graph the angle against the value in the array. i.e. the value a[50]=156.21 should graph to the point (50,156.21). Ideally as well I'd like for it to be joined up by a smooth curve of best fit, but I'll take what I can get, I can't seem to figure out how to plot it at all at the moment.

See code below:

restart;

for i from 50 by 5 to 85 do
ThetaBn := (1/180)*i*Pi;
s := cos(2*ThetaBn)*x+(2*sin(ThetaBn)*sin(ThetaBn))*sin(x);
a[i] := 180.0*fsolve(s = 0, x, 1 .. 6)*(1/Pi)
end do;

Thanks

The program below works fine, but comes up with an error message: wrong number (or type) of parameters in function \$.  I'm confused as the Maple 7 Help on 'convert, bytes' the \$ symbol is omitted.  The program works fine: it is just a little disconcerting, as this is just the start of a general Wordwheel program.

The error seems to be related to the textplot command - but why?

 > restart: # # # # # # # # # # # # # # # # # # # # # # # # # # # # # Wordwheel program - intended to be general # # # # # # # # # # # # # # # # # # # # # # # # # # # # with(plots): with(plottools): #Number of letters, including the ? sign nolett:=7: #Angle of arc for each letter ang:=2*Pi/nolett: R:=5: # Draw the circle c:=circle([0,0], R, color=black): #Draw the lines for i from 0 to nolett-1 do   lin[i] := line([0,0], [R*cos(i*ang),R*sin(i*ang)], color=black,   linestyle=1): end do:  #i #Upper & lower case alphabets #s_L := convert( [\$97..122], 'bytes' ):   #a - z s_U := convert( [\$65..95], 'bytes' ):   #A-Z #s_L[25];    tp1:=textplot([1,2,s_U[6]],align={ABOVE,RIGHT}): plots[display](c,tp1, seq(lin[i], i=0..nolett-1), scaling=constrained, axes=none);
 Warning, the name changecoords has been redefined Warning, the name arrow has been redefined Error, wrong number (or type) of parameters in function \$
 >

## three sides of a not flattened triangle...

E := proc (n::posint)
local L, x, y, z, p;
p := n; L := NULL;
assume(x::nonnegint, y::nonnegint, z::nonnegint);
assume(x <= y and y < =z);
for x from 1 to irem(p, 2) do
for y from x to irem(p, 2) do
for z from y to irem(p, 2) do
if x+y+z = p then L := L, [x, y, z] end if
end do
end do
end do;
return L end proc:
This procedure don't work. I would like E(9)={(1,4,4),(2,3,4),(3,3,3)} then E(2019), E(2022). Thank you.

## column name missing in FetchRow for Database[SQLit...

Is this documenation wrong?

https://www.maplesoft.com/support/help/maple/view.aspx?path=Database%2fSQLite%2fFetchRow

It says that calling sequence is

FetchRow( statement, column, valuetype  )

But below it only shows

 statement - prepared statement obtained using Prepare command valuetype - type of the output data, default is "auto"

With no column anywhere.  And none of examples show column in them.

And when I tried it by adding a column name that I know exist in my sqlite3 database, Maple gave an error that no such parameter allowed.

Does FetchRow support column name or is the above just a documenation error?

Maple 2019

## Metric in an index form...

Hello everyone!

Does anyone know if it is possible define a metric like the metric below?

## Why cannot 'solve' find the solution of some trivi...

I would like to understand why the 'solve' command is unable to find any solution to the system of equation { x^2=2, x^3=2*sqrt(2) }  (which obviously has a unique solution x=sqrt(2) ). The syntax that I used is
> solve({x^2 = 2, x^3 = sqrt(2)^3}, [x]);
and the output is the empty list.

I suspect that this is related to the presence of the algebraic number sqrt(2). Does anyone have a better understanding ?

I am using Maple version 2018.0, build ID 1298750.

Thank you.

## how can i write the title on the plot...

hi

how can i write the tittle on the plot exampe below pic

restart;
with(plots);
inequal({sqrt((1/2)*x) < y and sqrt(Pi/(2*x)) < y and y < sqrt(x) and y < sqrt(Pi/x)}, x = 1 .. 3, y = 0 .. 2);

## Shortcut or implicit operation?...

I discovered incidentally that the command  Matrix(3, 3, `-`) (the number 3 is purely illustrative) returned the same result than the command Matrix(3, 3, (i,j) -> i-j).
In the same way `+` realizes (i,j) -> i+j), `*` realizes (i,j) -> i*j), ...

More surprisingly `.` realizes (i,j) -> i*j while I'm in worksheet mode, with "old" maple input style, and that the command 2.3 does not answer 6 but concatenates 2 and 3.

Is this a known behaviour or an undocumented feature?

## Problems with IntegrationTools:-Change...

I bassically have one problem with an integral of the type:

and I want to change the integration variable. I've founded the IntegrationTools:-Change command, but it simply does not work.

givin the error:
Error, (in IntegrationTools:-Change) unable to determine new range for S

Any help is deeply appreciated.