Hi all,

I would like to plot a solution of differentiel equation in its three ranges [-10,-6^(2/3)/4[,[-6^(2/3)/4,6^(2/3)/4], ]6^(2/3)/4,10] .

When plotting using unapply(piecewise) I got an error like

Error, (in plot) offset to _Inert_LOCAL outside of range

See below my code.

Thanks for hellp.

HYP.mw

Hi,

The system below is successfully solved by using rfk45_dae method

I want to write the Runge Kutta scheme according to rfk45 method so as to have

S'=F(x,U,S,..), U'=G(x,U,S,..), ...

The presence of diff(S,x,x) in the second equation doesn't help me to definie F and G functions.

Thanks for your help 

Hi all,

Thanks for helping me to solve the problem below using Maple.

dsys := {(1-4*(diff(ln(v(z)), z)))*(diff(u(z), z))+((3/2)*z^{-1}-2*(3* z^{-1} *(diff(ln(v(z)), z))+2*(diff(ln(v(z)),z,z )))))*u(z) = 0, -z*(diff(v(z), z))-v(z)+v(z)^(1/2)*u(z) = 0, v(0) = 1, u(0) = 1, (D(v))(0) = 1/4, (D(u))(0) = 3/8}

When trying    sol := dsolve(dsys, numeric)

I got : Error, (in DEtools/convertsys) unable to convert to an explicit first-order system.

Note that the analytic solution for z<=0 is:

if z>-4   then  u(z)=(1+z/4)exp(z/8) and   v(z)=exp(z/4)

else u(z)=0  and v(z)= (-4/z)exp(-1)

Regards

Hi all,

I would like to know how could I plot an ODE for 3 values of a parameter in the same figure.

sol:=dsolve(dsys,numeric,parameters=[t]);

p:=proc(t)sol(parameters=[t]); plots:-odeplot(sol,[x,f(x)],-1..0,_rest) end proc;

p(-1); p(-0.5); p(-0.1);

Here, I have 3 figures one for each value. I used with(plots): display(p(-1); p(-0.5); p(-0.1)). But doesn't work.

Thanks for your help.

Hi,

I try to solve a system of two second order non linear ordinary differential equations using Maple that I expect to find singularities as blow-up points.

So, I would like to know how to compute values of singular points when existing.

Thank you in advance. 

ode1: -0.1*diff(u(z),z$2)+(z-2*diff(v(z)^-1/2,z))*diff(u(z),z)+(3-2*diff(v(z)^-1/2,z$2)*u(z)=0

ode2: 0.1*diff(v(z),z$2)+0.01*z*diff(v(z),z)+0.02*v(z)-u(z)*v(z)^1/2=0

Ics: u(0)=0, v(0)=0, D(u)(0)=0, D(v)(0)=0