Hello

I have a matrix, let's call it A. I want to define a new matrix by taking every n-th row in the A matrix. How do i do that?

For example,

A= | 2 3 5 |
     | 9 2 1 |
     | 5 1 2 |
     | 1 8 9 |

 

the B, if n=2, is equal to

| 2 3 5 |
| 5 1 2 |

I'm trying to model Conway's game of Life and I keep running into the same error mesage. I've narrowed the problem down to this line of code

S0 := [[0,0,0,0],[0,1,1,0],[0,1,1,0],[0,0,0,0]];
n:=4
X:= Array(0..n-1,0..n-1,S0)
Error, bad index into Array

I don't know what this error message is or why I'm getting it, any help would be appreaciated.

Hi, sorry to post this as I have read past topics about roots but havent really understoond much.

I have an equation that gives 8 roots. some of them can be real and some can be imaginary. how do i list them separately? I attach the worksheet...

 

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Hi to all

I want know that can we slove the following equation

=0

where

F(l)= coth(l*(S0)))/coth(l*(S0-1)));

Is this possible from mathematical point of view?

 It make any sense to slove the above equation?

 

When simulating an electrical circuit I decided to eliminate a subsystem block but later changed my mind. Now I'm unable to use the same name for the subsystem block as before despite the fact that there seems to be no place where it is used. Always an error "The name blabla is already in use". Can I somehow list all the names and the places where they are used?

I have been trying to do this for some while now but am not having much luck.

Basically what I need is a hermitian matrix, with real values on the diagonals X~N(0,1) and complex values on the off diagonals X~N(0,1/2)+i*N(0,1/2)

Obviously as its hermitian I need Xij = Xji*
 

I have tried a few things but can't get anything to work correctly, in my latest attempt I decided to try and construct the 2x2 case from scratch using if and for loops;

for i to n do

for j to n do

if i <> j then

restart; with(DEtools); phaseportrait([(D(x))(t) = -.1+x(t)^2-x(t)*y(t), (D(y))(t) = y(t)^2-x(t)^2-1], [x(t), y(t)], t = -10 .. 10, [[x(0) = 0, y(0) = 1], [x(-2) = -2, y(-2) = -1], [x(0) = 1, y(0) = 0], [x(0) = 0, y(0) = 0]], stepsize = 0.5e-2, scene = [x(t), y(t)], linecolor = t, x = -4 .. 4, y = -3 .. 3) I want to explicitly draw the hyperbola with arrows in the direction of the vector field. How do I obtain this? With the initial conditions I get solution curves that I dont want.

# Hello!
# I've been trying to replace one expression into another, which includes the derivative of a quotient, but algsubs doesn't work and I don't know why.
# To make it simple, I want to replace a expression from rho into the expression for q_x. Let's say rho is a function of alpha.
>
> restart;
> alias(rho = rho(x, y, t)); alias(rho_an = rho_an(x, y, t));
> alias(p = p(x, y, t));
> alias(q_x = q_x(x, y, t));
> alias(alpha = alpha(x, y, t));
>
>
> rho_an := alpha;

Can someone help me please? I cant find what is wrong. thank

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Nash

how can i understand calculus own my own. and i'm a lazy student.

I need to write a loop within a loop for something like this;

for i from 1 to n for j from i to n do;
A[i,j]:= rand();
A[j,i]:= A[i,j]

end do; end do;

(just random sample code, not what I need to do)

But I don't want the loop to carry this out for when i=j ie. A[i,i] for i = 1 to n. How can I do this?

This is on Simple Harmonic Motion. I have
KE= 2*v(t)^2 ,
PE= 3*x(t)^2 + 4*x(t)^4.       and I also have given
diff(x(t),t) = v(t).

I needed help plotting it because I know that TE = PE + KE is a constant and I just want to plot it into a straight line. ( I have simplified the equations so don't worry about the equations being wrong).

 

Help Needed, really appreciated.

 

Thanks, 

 

Hi,

I tried to find the limit of the following equation using l'hopital's rule, when sigma approches to zero find i couldn't find it.

Now i want to use Taylor series to find the limit of the following equation, when sigma approches zero.

Hello! And thanks for looking and helping!

I've been working on programming an algorithm that requires that I find the polynomials A, B
such that Af + Bg=Res(f, g, x) [the resultant] where f and g are given. In all my searching I couldn't find something that would spit out A and B for me. No luck that route so...

Hi!

I've a problem with maple. I wonder to see the visualisation of the solutions of a system of partial equations :

with(PDEtools);
EDP := [diff(s(x, y, t), t) = -.45*i(x, y, t)*s(x, y, t), diff(i(x, y, t), t) = .45*i(x, y, t)*s(x, y, t)-.2*i(x, y, t)-.7*(diff(i(x, y, t), x)+diff(i(x, y, t), y))];
IBC := {s(0, y, t) = 1, s(x, y, 0) = f(x, y), i(x, y, 0) = g(x)};
f := proc (x) options operator, arrow; 1-g(x) end proc; g := proc (x) options operator, arrow; piecewise(x = 20, .2, 0) end proc

 

But when I write :