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These are questions asked by sarra


I need your help .. I solve a system and I get the error Warning, solutions may have been lost.

The maple code is attached.

Thank you for your help.


Dear all:

hello everybody;

I need your help to solve the system f(x,y)=0, and g(x,y)=0, such that there some parameter in the system, also all the parameter are positive and also our unkowns  x and y are also positive.

I try to write this code. I feel that under some condition we can have four solution or three or two. I need your help. Many thinks.


I need your help to display the matrix generated by a lenear system.

The linear system is okay, well written, but  there is an error in generate matrix, I get the wrong matrix.

Thank you very much for your help.

Dear all

I need your help to create a band matrix of n block,   and each block of the matrix is given by:

A=[[1,2,3];[2,1,3]; [3,2,1]]:

Thanks for your help




Thank you very much for your idea in previous discussion: this is the link.

I asked how can I plot the phase portrait of this system

Sys1 := {diff(r(t),t) = r(t)^2*sin(theta(t)), diff(theta(t),t) = -r(t)^2*(-2*cos(theta(t))^2+1)};

I get this answer:


1) For me it's not necessary to give an initial condition to plot the pharse portrait.

2) What is the line in this phase portrait.

3) Here, I try a second method using Matlab code, I get:


and this is the code:

[r, theta] = meshgrid(0:pi/4:2*pi, 0:pi/4:2*pi);
rdot =r.^2.*sin(theta) ;
thetadot = r.^2.*(1-2*sin(theta).^2);

the arrow in the phase portrait are not the same.

Can someone give me more clear information about this problem.

Many thinks.


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