Dear all,

I come up with a problem. When I execute the following commands in 2d mode, error occurs:

restart; with(MTM); with(plots); r := .125; omega := .3; l := 1; m := 4.5; IG := (1/2)*m*r^2; A := Matrix(4, 4, {(1, 1) = 0, (1, 2) = 0, (1, 3) = 1, (1, 4) = 0, (2, 1) = 0, (2, 2) = 0, (2, 3) = 0, (2, 4) = 1, (3, 1) = 0, (3, 2) = r*omega^2*(IG+m*r*(r+l))/(l*IG), (3, 3) = -2*ldt/l, (3, 4) = 0, (4, 1) = 0, (4, 2) = -r*omega^2*(IG+m*(r+l)^2)/(l*IG), (4, 3) = 2*ldt/l, (4, 4...

Dear all,

I've got a Vector,

>V:=<xt[1, 1]*xt[1, 2]*alpha>;

and what I want to get is the elements in V which has xt[2,2]. In this case, <NULL> is what I am looking for.

I tried the following line:
> select(has,V,xt[2,2]);
     The result is Vector(1, {(1) = NULL});
when I tried
> select(has,V[1],xt[2,2]);
     The result is 1.
I have no idea where this

Dear all,

I have a pair of equations,

-xt[1,1]+a*tanh(xt[1,1])+a[12]*tanh(xt[2,1])=0,-xt[2,1]+a[21]*tanh(xt[1,1])+a*tanh(xt[2,1])=0

and I want to calculate xt[1,1] and xt[2,1];

when i use

solve([-xt[1,1]+a*tanh(xt[1,1])+a[12]*tanh(xt[2,1])=0,-xt[2,1]+a[21]*tanh(xt[1,1])+a*tanh(xt[2,1])=0],[xt[1,1],xt[2,1]]);

warning comes out," Warning, solutions may have been lost", and the solution [0,0] I am looking for is really lost.

Hi, everyone.

I have got a question. There are n variables q[1],q[2],...q[n]. Each variable can take the value of 1,2, or 3, and I want get all the possible values of sum of these n variables,i.e. sum(q[i]...i=1..n). 
When n=2, I  write the procedure as follows:
    for q[1] from 1 to 3 do
      for q[2] from 1 to  3   do