Hello,

I have a ode system which I use dsolve/numeric for it?

By default dsolve use rkf45 but the result is not very exact. The error is high.

How can I make dsolve more accurate?

Which method I have to use?

It is initial value problem that I use dsolve/numeric for it.

Thanks so much.

Bye

Problems: Calculate Fourier Transforms of:
>
> f(t)=1 for (1<=|t|<=2) and 0 otherwise
>
> f(t)=cos wt[H(t+1/2T)-H(t-1/2t]
>
> f(t)=exp(at) (t<=0), (a>a) and exp(-at) (t>0)
>
> f(t)=exp(-at) sin wt H(t)
>
> note: w is omega and T is Tau, H is Heaviside
 

Not sure how to do these problems with maple.

I need help making a 3D plot of a numerical solution to Euler's Equation for Rigid Bodies(Non-linear Differential Equation). The solution to this equation are the angular velocity components w1,w2,w3. I am able to plot each component using the following commands, plots[odeplot](numericalsol,[t,w[1](t)],0..20); plots[odeplot](numericalsol,[t,w[2](t)],0..20); plots[odeplot](numericalsol,[t,w[3](t)],0..20); However, how do I make a 3D plot using these numerical solutions?? Any help is greatly appreciated.

Sometimes I've seen manipulations like this:

dx/dt = dx/dy dy/dt

in which the symbols of the derivatives are multiplied and cancelled like terms in equations. I can't remember nor find the justification for doing this. What's the explanation?

I can't get Maple to do this for me. If I make x an expression of y and y an expression of t, then it substitutes the expressions into the arguments, and I get a nonsensical result:

> y := t^3;
3
t
> x := 'y^2';
2

Guys, I'm stuck on a simple silly problem.  I suppose I have one of those senior moments but in any case  ...

All I was trying to do was derive an equation from a simple word problem I made up.  Specifically it has to do with the fact that it's costing me more to buy efficient energy saving flourescent bulbs than to use those ever so energy inefficient incandescent bulbs.  But it turns out those inefficient bulbs is the cheaper route.

Basically it's a cost analysis problem.  Anyways here's how it goes. 

Hi:

I often need to change a few parameters and rerun the whole worksheet. In some cases however, some of the sections should not be executed. Is there a way to quickly comment/uncomment out a given section? If so, how?

thanks.

Hello all,

I have an ODE system called RedSys which is below and incons1 which is its initial condition.

When I want to solve this system by dsolve numeric with this command:

dsolve((convert(RedSys, set)union incons1), numeric, implicit = true);

I face an error which says :

system should be linear in leading derivative. However when check I do not see any non linearity.

could you please let me know what should I do to solve this system by dsolve/numeric?

Thanks so much,

 

Hi

I have a problem with the fact that maple not always knows the difference between pi and -pi. Try for example these three lines:

> evalf((-5-2*I)*(exp(-(.999999999*I)*Pi))^(1/2-0.8e-1*I)); 

> evalf((-5-2*I)*(exp(-I*Pi))^(1/2-0.8e-1*I));

> evalf((-5-2*I)*(exp(I*Pi))^(1/2-0.8e-1*I));

They have significantly different results where the line with the exp( - I*Pi) is interpreted as exp(I*Pi).

Is there anyway to avoid this?

I use maple 13

Thanks in advance

Best regards
Brian

In a Maplet, how do I access an expression entered into a MathMLEditor to use as a Maple expression (to plot, evaluate, simplify etc.)?

Hi.  I want to plot the function U in terms of x and y,

U :=2*diff(p(x,t),x)*diff(q(y,t),y)/(p(x,t) + q(y,t) + a[0])^2;

where

I would appreciate if anyone could solve this problem. (please see attached pdf or mw file )
The error messages is:  Error, (in ExecuteQuery) unknown API type  (I am trying to access data from a SQL server)

Download 8342_Maple is being Stupid.pdf
View file details

I used the solve command to solve for the unknown b , i do have the solution listed in the book...but when i try to solve it as follows

solve((tan(Pi/18)=(2*cot(b)*((3.4^2)*sin(b^2)-1))/((3.4^2)*(1.4+cos(2*b))+2)),b);

since maple takes values in radians(10 deg)

i get the message as "solutions may have been lost"

Am i doing anything wrong ?

Hi.

This one is rather simple. Anyway I do not get the right way to do it.

I´d like to redefine showassumed and set it to zero.

Can anyone give me an example how to do it?

Thanks.

I tried the following:

restart;
with(Statistics):
X1 := RandomVariable(Binomial(n, p)):
DARA := t->piecewise(0<t,log(t),0):

0 < n, n::posint, 0 <= p, p <= 1:
 

ExpectedValue(DARA(X1));                                        
g1 := simplify(%) = DARA(s);
k1 := solve(g1, s);
 

Hi.

Does anyone know, why or when to use the assume command as opposed to just defining the assumptions?

e.g.

instead of typing:

assume(0 < sigma);

i could just write:

0 < sigma;

right?