In the following code Maple simplifies the last expression different, based on whether assume(mu::real, sigma>0) is set or not.

The point is, that the assumptions got -to my mind- nothing to do with the displayed results.

Why does Maple do such weird things?

Here is the code. The last output is different based on whether the '#' before assume(mu::real,sigma>0): is set or not:

restart;
with(Statistics):
Y9 := RandomVariable(LogNormal(b, c)):

I discovered, that Maple did substitute every single parameter but c!

Anyway, when I isolate the problem and do not assume anything for mu and sigma, the problem does not occur.

Therefore I print here the complete relevant code.

Is there a way to "convince" Maple to do those trivial substitutions of c also, without seperating each problematical expression?

Here is the code:

restart;
with(Statistics):

#Definitions and assumptions

My problem is the following:

deq1:=2*[(y(x)*(diff(y(x), x, x))-1)/sqrt(1+(diff(y(x), x))^2)+(diff(y(x), x, x))/(1+(diff(y(x), x))^2)] = cos(x);
I do this way (error anyway):
deq := (y(x)*(diff(y(x), x, x))-1)*(1+(diff(y(x), x))^2)+(diff(y(x), x, x))*sqrt(1+(diff(y(x), x))^2)-cos(x)*sqrt(1+(diff(y(x), x))^2)*(1+(diff(y(x), x))^2) = 0
sol := dsolve([deq, y(0) = 0, (D(y))(0) = 0], y(x), numeric, range = 0 .. 3)

So, my question is, how can I determine the integral of the left side of deq1? ...

How do I keep Maple from changing the variable xi to the greek letter?

Hello,

I have this differential equation:

deq := (diff(y(x), x, x))*y(x)-1+x*y(x)^2 = cos(x);

sol := dsolve({deq, y(0) = 1, (D(y))(0) = 1}, numeric);

After that I have a numerical solution for y, and for diff(y(x),x). But I would like to plot diff(y(x),x,x). (and then diff(y(x),x,x)+diff(y(x),x)*cos(x)). How can I do that?

Any help will be appreciated,

L

Hello there,  How can I compile this? I used   boundarycompiled := Compiler:-Compile(findboundary)    but this didnt work. Thanks in advance

> findboundary:=proc(a,b,c,d,e,f,g,h)  ;
> global A,B,lowerbound,upperbound;
> A, B := solve(a = b, x), solve(c = b, x);
> x1a, x1b := evalf(solve((x-e)^2+(a-f)^2-g^2)); if x1a < x1b then minx1, maxx1 := x1a, x1b else minx1, maxx1 := x1b, x1a end if;
> x2a, x2b := evalf(solve((x-e...

Hi. I have to solve the following differential equation numerically

f := [(diff(y(x), x))*(diff(y(x), x, x))/sqrt(y(x)^2+diff(y(x), x))+diff(y(x), x, x)] = x^6

dsolve({f, y(0) = 2, (D(y))(0) = 1.5, (D(D(y)))(0) = 1}, y(x), numeric, range = 0 .. 10)

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

I don't know what to do, I've read help and work on this for 3 days now.

Hey,

i am completely new in working with Maple. I spent the past 2 days to find a solution to my problem, but wasnt successfull.

Here is what i wanna do:

i have a function with 3 Variables and i wanna take the total derivative of this function.

Then i wanna know if the derivative is positiv or negative.

The only thing about the variables i know is that 2 of them are between 0 and 1, and the other variable...

Hi

I guess I should know this but what is the difference between a Matrix and an Array in Maple?

thanks

I've been given the relationship:

R*sqrt(sigma)-1-(1)/(4)*(l-(2*kappa*R^2)/(R*sqrt(sigma)))/(1+coth(R*sqrt(sigma)))-kappa*R^2/6+m/(2*R), for the particular case where m=l=0, and where

R=exp[(kappa*(R^2))/6]. On a sketch of R vs kappa, apparently sigma >0 on the lower branch, but there should be some sigma < 0 on the upper branch.

To attempt to solve this whole problem, I use the following commands:

restart;with(plots):

Please help plot solution of ODE in polar coords or tell how can i define a piecewise function that will make me able to plot the right and left side of singularities.

>sys1:=diff(r(t),t$2)=2*cos(teta(t))/r(t)^3,diff(teta(t),t$2)=sin(teta(t))/r(t)^3;funcs:=[r(t),teta(t)]:InC:=r(0)=1,teta(0)=15,D(r)(0)=0,D(teta)(0)=-2;

>FNUM:=dsolve({sys1,InC},numeric,funcs);

>odeplot(FNUM,funcs,t=0..230,numpoints=2000,coords=polar,view=[-20..20,-20..20]);

Thanks

Hello

I have the following nonlinear differential equation:

deq := (diff(y(x), x, x))*y(x)-1+x*y(x)^2 = cos(x);

I solved it numerically:

sol := dsolve({deq, y(0) = 1, (D(y))(0) = 1}, numeric);

ysol := proc (x) options operator, arrow; rhs(sol(x)[2]) end proc;

plot('ysol(x)', x = 0 .. 5);

but I would like to substitute it to the left side of deq and plot it, to be sure that it's plot is the same as cos(x).

My question is in regards to the events feature in dsolve numeric.

At a particular event time, I was wondering if it is possible to call a previous moment, that is something like

eq:={ diff(y(t),t) = y(t) };

ic:={ y(0) = 2 };

de:=dsolve( eq union ic, numeric, events=[[ t =5, [ y(t) = y( t - 2 ) ]]],range=0..10);


If it is possible to "globaly" declare previous steps of the dsolve, I believe that the above de would work. However,...

Hi everyone, here we are again with more serius issues this time.

I have a system of DE to solve. My system is made of coupled 3 PDE`s with 1 ODE. My problem is that the computation is aborted due failure at memory allocation, here is the message:

"Error, (in factor/nexteval) Cannot Allocate Memory (size=151060480)"

I`ve checked the kernelopts about datalimit and its already infinity. My computer is a Turion x2 with 4Gb of Ram (system...

Hello,

I want to evaluate an integral over the Dirac function with basically the following assignments. (I had some troubles parsing here...) Then I want to plot function rho(epsilon). What I get is just an empty graph with nothing displayed although test has only values in the range -3...3. I am pretty new to maple and don't know how to compute this in another way.

> test(x,y,z) := .2686733768*x^2+.2686733768*z^2-.2178281566+.2686733768*y^2+(-1)*1.000000000*sqrt...