175 Reputation

15 years, 64 days

system of complicated ODEs...

Maple

Dear guys! I want to solve a system of ODEs but I have some problems. Plaese have a look and let me know:

> Omega_m0 := 0.22: Zeta_m := 10^(-4): n := 0.35: h := 0.63: omega := 1:

> eq := z-> 1 = H^(2*n-2)*(1-Omega_m0)/(h^(2*n-2)) + h^2*Omega_m0*(1+z)^3*(1+Zeta_m*exp(-2*psi(z)))/(H^2) + omega*H^2*(1+z)^2*(diff(psi(z),z))^2/(6*h^2);

> yp := implicitdiff(eq(z), H, z);

> ode1 := diff(H(z),z)=subs(H=H(z),yp);

> ode2 := H(z...

how can I plot a list of data...

Maple

Hi all! I have a list of data. I can use pointplot to plot them. Now, whatshould I do if I want to connect (join) these points toghether like an ellipse or rectangle or others form? For example:

S := [[1,1], [3,1], [4,2], [3,3], [2,3], [1,2]];

thanks

why does the results change?...

Maple

Dear guys!

I'm solving an equation and then by its results I solve an integral, but I'm doing that for many initial conditions in a for loop. The problem is that when I change the limits of loop (or initial conditions) the result of integral in two for loop for a same initial condition are very different. What's the problem?

Thanks!

why different results?...

Maple

Dear guys! Please look at the two following ways to solve a same equation and tell me why the results are different:

The initial conditions and the equation for both ways are:         m := 0.22: k := 0.03: n := 0.35: h := 0.63:

> eq := z-> 1=(m*(1+z)^3-k*(1+z)^2)*h^2/(H^2)+(((2*n-1)-(k*(1+z)^2*h^2/H^2))*((1-m+k)/(2*n-1+k))*((((H^2/h^2)-k*(1+z)^2)/(1-k))^(n-1))):

The first model:

> yp := implicitdiff(eq(z), H, z):

about subs in solving ODE classically...

Maple

Dear guys! It seems to me that we can not use "subs" after solving an ODE system by method=classical[rk4]. Am I right? If your answer is yes then how should Ido instead?

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