## Documentation of GraphTheory[Trail] missing?...

To whom it may concern:

It appears that 'GraphTheory[Trail]' is missing from the Maple help function. Am I overlooking something? I am running Maple 12.01.

Cheers

Roberto

## How to get the inflection point of a curve or a ex...

Dear all,

I really really need a command for getting the inflection point of a expression. Thank you very much!:)

Best regards.

## The maple doesn't have response ?:)...

Dear all,

I use solve() to sove a equation group. when I typed the command and press Enter. there is no response even a error or fail. what is the reason?

BTW: the equation is complex.

Best regards!

## mean of a matrix...

What's the standard (or a cool non-standard)  way to compute the expected value of a matrix, e.g., a covariance matrix? Using this code:

restart; with(LinearAlgebra): e1 := Statistics:-RandomVariable(Normal(0, sigma)); L := [seq(e1*cos(pi*t), t = 1 .. 3)]; convert(L, Matrix); Transpose(convert(L, Matrix)); M := Multiply(%, %%); S := map(Statistics:-Mean, M)

how do I simplify S to the matrix of +/- one's and factor out sigma^2 outside the matrix? Thanks.

## Removing Components from Subsystems Library...

When a user drags and drops a component from the pallette, a copy of the component is copied into the subsystem library located in the lower right of the screen.  This is handy if used again so that the user does not have to drill down into the pallettes repeatedly.  But, after a while the copies accumulate in the subsystems library, and it would be nice to selectively delete them if the user knows they will not be used again.  I have not found any way to delete the built in components copyied into the subsystem library.  I suppose it is childishly simple, but the operat

## points and triangles...

Given four points in 2D, P1=(0,7), P2=(1,-12), P3=(7,0), P4=(10,-9), solve the following problems:

(1) Determine if P1, P2, P3 form a triangle;

(2) If they form a triangle T, determine if T is isosceles (two sides equal) and plot T;

## How to change the font in maple:(...

Dear all,

I am a newer for Maple. When I want to type some command in maple, I find that the default font is not very good. I try to change it, but when I type next exe group, I find  that the default font is recovered~~ How to change it forever?

Best regards,

## Trouble with Nested Loops...

I am having trouble with the following sum not adding properly:

sum(sum(sum(1/k!/j!/m!,k=2-m-j..2-m-j),j=0..2-m),m=0..2);

By my hand calculations, this should be 4 (?), but maple says it is zero. If we remove a factorial (like below) we will get a non zero sum. What am I doing wrong,or is this a bug in maple?

sum(sum(sum(1/k!/j!,k=2-m-j..2-m-j),j=0..2-m),m=0..2);

thanks.

## finding 2-D scalar potential of vector field with ...

I'm having trouble figuring out how to find the 2-D scalar potential of a 3-D vector field projected onto a plane.  The vector field is computed on the plane, coordinates (X,Y), as a vector function with arguments (X,Y,u), with 'u' being a parameter.

After invoking the VectorCalculus package and specifying

SetCoordinates(cartesian[X,Y]),

## extract and assign...

I use the solve command to solve a quadratic equation. I get two outputs and want to assign the second output to the variable x. How can I do this?

Quadratic equation is 3x^2 - 9x+11

## Data Export to Textfiles...

I have calculated data in form of a matrix. The corresponding x- and y-values are given in two lists (see attached file).

Now I would like to export the data to a textfile to use it in another program. The problem is, that I need the following format (name_listA[i]_listB[j]= is a text string where the corresponding x- and y-values are integrated)(values[i,j] is the number out of the matrix):

name_listA[1]_listB[1]= values [1,1]

name_listA[1]_listB[2]= values [1,2]

etc....

## Solving Non linear system of equations for a range...

hi guys, i have the following set of equations e1='a2+a3+a5+a6-1=0'; e2='2*a1+2*a4+4*a5-1.6-2*0.2=0'; e3='a2+2*a3+a4-0.77-0.2=0'; e4='(K1*((a1+a2+a3+a4+a5+a6)^2/4)*(a5*f))-(a1^3*a2)=0'; e5='K2*a2*a4-(a1*a3)=0'; e6='K3*a4*a6-(a1*a2)=0'; symbolic a1,a2,a3,a4,a5,a6 I can slove these set of equations for known values of K1,K2,K3 but i have a set of values for K1,k2,K3 (35 values) ie K1=[1 2 3 4.......35] K2=[1 2 3........35] K3=[1 2 3 .....35]

## How do I use recursion and get Maple fast?...

I have the next problem, i need to  use recursion to make the equation E(x+1)=E(x)+(E(x)*(P-E(x)))/P*10 with P 15000 and E(1)=1, i put for example E(20), but maple only use ram, but doesn't do anything.

Thanks

## Solving a Linear Matrix...

I got a set of 8 variables and 8 equations, i need to solve them. I tried using "fsolve" but there are too many variables and too many equations. I thought I can try it using linearalgebra.

## Sorting a list of lists...

Dear all,

I am using version 12. I would like to sort a list of lists of  integers in respect to some of the terms of the sublists.

For example, the list

[  [3,5], [2,10], [9,1], [4,2], [7,3]  ]

would be sorted as:

[  [9,1], [4,2], [7,3], [3,5], [2,10]  ]

in respect to the second variable.

Actually, I found that the sort command with  the 'lexorder'[n] option would exactly this, except that it

seems that it doesn't work with numbers, but only with letters.

Any ideas?

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