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Hello, I have a problem with plotting graphs with a constant.. I have one system of equations and one another equation:






I need to compare theit curves.

k and C are constants. I thought it is alright if I would remove constants, BUT there is one in the power, so I have no idea what to do.. 

I just tried to plot the system, but it doesn't work either:

I'm solving a system of ordinary differential equations numerically, I used the dsolve(system,numeric) to do it. I have also plotted the solutions. Now I want to know where does this solution cross zero and use this value for later computations, is there a way to do it? 

This question is, as I think, equivalent to how to find the roots for a curve expressed in numerical arrays.

Thank you!

I know how to solve system of differential equations numerically, but now I want to know how to set a bound on the solutions. 

For example, if my system of DE is like this:   dx/dt = x+y   dy/dt = x-y    , solve x and y in t. 

I can solve this without any restriction on x and y, now I need to know how to bound x and y, e.g. x can only fall in the interval [0,1]


Thank you very much!

equation value changes...

February 09 2013 AliKhan 10

Hi guys,

I have the following complex equation,


It gives a value which is constant for frequency upto 3000 Hz, i.e. if I run the solution again keeping all the values constant the result is the same  BUT   When I change the frequency to 15000 Hz, the equation still give me the result but every time its different when I run the program with constant values.

I have a set of 9 equations and 9 unkowns. These equations are massive 9th order polynomials. The equations themselves are contained in a vector called "C" in the .m file that follows:

Cvector_with_a.txt    (please rename the .txt file to .m since this forum doesn't seem to allow the upload of .m files)

In order to solve the eqautions, you must first set the values of two extra...

Hi in trying to solve these coupled differential equations i get a weird error:


> t := diff(X(x), x) = -(1-6*R(x)^(1/2))^(1/2)*x*X(x)/(X(x)*x+R(x))^(1/2), diff(R(x), x) = (1-6*R(x)^(1/2))^(1/2)*x^2*X(x)/(X(x)*x+R(x))^(1/2);
/ (1/2)\
d \1 - 6 R(x) / x X(x)
--- X(x) = - -----------------------------,


I have a set of diffferential equations: 

> U := diff(X(x), x) = -10*(1-5*T(x)^2)^(1/2)*x*X(x)/(X(x)*x+R(x)), diff(R(x), x) = 10*(1-5*T(x)^2)^(1/2)*x^2*X(x)/(X(x)*x+R(x));
/ 2\
d 10 \1 - 5 T(x) / x X(x)
--- X(x) = - ----------------------------,
dx X(x) x + R(x)

Dear all, I am new here, so I am sorry in advance if I make some mistakes. The problem here is how to transform

system of 2 differential equations 4th order to the system of 4 diff equations second order, or how to reduce system of 2 equations 4th order on two equations second order with vanishing solutions which I choose because they are big. Here is example



I am trying to solve a problem in theoretical applied mechanics in which I need to find the solution for 5 unknown but I have 6 equations. None of the equations is redundant and I need the solution of the variable to satisfy each of the equations.

These are the equations 


Hi I have three differential equations: 

u := diff(P(t), t) = -7*10^(-8)*P(t)*t/(P(t)*t+R(t))^(1/2),

diff(R(t), t) = 7*10^(-8)*t^2*P(t)/(P(t)*t+R(t))^(1/2)+600*(Z(t)^2-10^5*t^3*(1/(1.15*10^12))^(2/3)*e^(-1.15*10^12))/(t*(P(t)*t+R(t))^(1/2)),

diff(Z(t), t) = -4*10^5*(Z(t)^2-10^5*t^3*(1/(1.15*10^12))^(2/3)*e^(-1.15*10^12))/(t^2*(P(t)*t+R(t))^(1/2))


and i want to solve them with initial conditions:

initial := R(0) = 0, Z(0) = 0, P(0) = P;

Hello all,

I have the state-space form of a dynamics sytem:

X_dot = AX+B.U

Y= C X,

The initial conditions of the outputs (Y0) are also given.

A is 7x7 known matrix,

C is 14x7 known matrix,

B = 0;

The problem is that it's too long to write down every equations (14+7 eqns) and variables in "dsolve" function

Would you please show me the shorter way to solve a very large state-space system?

I really appreciate your help.

Dear friends

I solve a rectangular system of equations AX=B   where A from order 3m+1x2m      X from order 2mx1       B from order (3m+1)x1   where  m=400, by LeastSquare or by multiply by A^T  


let M=A^T*A

then     M*X=A^T*X                 finally               X=M^-1 * A^T*X

I use the eqn feature from Maple to generate troff output.

Each equation is longer than one line. How does one get the eqn/troff
combination to automatically break the equation into multiple lines.

(I tried finding the division point myself and could not do it. I am
generating the output and I have a perl script that puts together the indivdual
equations into the document to be printed. Thus, I need something automatic)

I tried Google and...

Hi all.. Just purchased the maple 16 today. When i tried to enter a few equations, i relised that equals sign does not work for the equations. I tried '' ctrl+= '' but the letters on the screen get minimized that time. I just can't do the thning. My OS is win7. It does the job when it comes to calculate 2+3 or something like that. You get the answer when you press enter. But when it comes to variable eq.s like x+3=2 or 2x+3y=4 when you press enter, nothing happens. ıt just...

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