It seems that the forum activity of the user  Markiyan Hirnyk   is no longer accessible.
Is it a site problem?

My goal is to find a positive linear combination of a vector vec over a set of vectors M1,...,M6. In this case the Mi are the columns of the matrix M.

My reasoning is: solve the linear system M.x=vec, which gives me a parametrized solution, then check if there is at least one positive solution.

M:=Matrix([[3, 0, 2, 2, 1, 1], [-1, -1, 0, -1, 0, -1], [0, 3, 0, 1, 1, 2], [3, 0, 1, 2, 0, 1], [-1, -1, -1, -1, -1, -1]]);

vec:= Vector[column](5, [3, 1, 0, 0, -2]);

x:=LinearSolve(M,vec, free = s);

But when I use the LinearMultivariateSystem function I get an error

LinearMultivariateSystem({x[1]>=0, x[2]>=0, x[3]>=0, x[4]>=0, x[5]>=0, x[6]>=0},[s[1],s[2],s[3], s[4], s[5],s[6]]);
Error, (in Utilities:-SimpleAnd) invalid input: a string/name list is expected for sort method `lexorder`

Can anyone tell me what is wrong in the code?

If I manually type in the expressions, and use variables such as x,y,z... then I get the solution, but I want to put the function into a loop.

I am very open to suggestions on how to decide if a vector is a positive linear combination of other vectors.

Maria

Hi

I have the values of of a function A(x,y,z) in 3d cartesian coordinates as [x[1],y[1],z[1],A(x[1],y[1],z[1])], [x[2],y[2],z[2],A(x[2],y[2],z[2])], [x[i],y[i],z[i],A(x[i],y[i],z[i])],etc...where i vary from 1 to 300 (or higher).

How to plot A(x[i],y[i],z[i]) in 3d.

Thanks

I am trying write a code for this question at here 

https://math.stackexchange.com/questions/170319/how-many-triangles-with-integral-side-lengths-are-possible-provided-their-perim/170325#170325

but I got the wrong answer. This is my code.
 

restart; 
L := []; 
for a to 18 do
 for b to 18 do 
for c to 18 do 
if a < b+c and b < a+c and c < b+a and a > abs(b-c) and b > abs(a-c) and c > abs(a-b) and a+b+c = 36 then
 L := [op(L), [a, b, c]] end if end do end do end do;
 nops(L); 
L

I got 136 triangles. This is a wrong answer. How can I repair my code?

how I can pdsolve these equations?

moadelat.mw

Download moadelat.mw

I have multiple accounts. I would like to delete them. Please tell me how to delete it. Thank you.

How can I plot functions Vc=(0.5+t)^n

with t=z/h, 

Hai any one help me to plot the curves and remove the errors  i am attaching the codes and  sample graph. thanks in advanced.
 

test.mw

Hi all,

I'm struggling with solving a delayed differential equation with time-dependent delay.

I have already use dde solver with matlab and find it cannot reaches my numerical accuracy. 

Does maple can solve this problem? I explore a little bit and don't find there is a document to guide how to tackle with this problem.

Constant delay cannot solve my problem.

Thank you very much,

Peter

Is there a solve(identity ...) command for systems? I have 4 identities in the variable t.
They are Q1, Q2, Q3, Q4. I try solve(identity(Q1,Q2,Q3,Q4),t), A, B, C, D), and other forms of it, but
nothing works.
Thank you!

maplatha
 

I solved an ODE numerically. Code: question_(2).mw

delta*(M(t)*diff~(X, t$2)+C(t)*diff~(X, t))+K(t)*X=f(t)

How to calculate X(t) for different values t and to create a table like following. 

I tried to solve an equation with a A0^2*v0 + .....................= 0 with 0 as a subscripted Index. The value of A0 was 0.35.

Maple returned the result with 0.350 as a variable with subscripted 0 and no numerical result.  When changing the variable to A0 without subscripted index 0 Maple returned the numerical result correct.

Hi there!

I am trying to calculate Eigenvectors of Matrices, Maple does not seem to understand that, however. I have used the structure of the example in the "help" section

A := `<|>`(`<,>`(-1, -3, -6), `<,>`(3, 5, 6), `<,>`(-3, -3, -4));
v, e := Eigenvectors(A) 

and even the example itself, it doesn't work. Maple always responds with   

"Error, (in Matrix) triangular[] storage expects name parameters"

What can I do?

I am trying to do taylor series expansion around the critical point, but I keep getting an error, because I think Maple is taking my critical point as function {x(t) = 5, y(t) = 10}. I would like to get just the output of x(t)=  from the list of critical points. Ex. Does anyone know the maple code to get "5" and "10" from the list of critical points without typing in 5 and 10.