J4James

320 Reputation

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8 years, 33 days

MaplePrimes Activity


These are replies submitted by J4James

@Muhammad Usman 

You need to watch your language. This is community based site. People here are not paid (volunteers) to answer your wishes. 

You should present your problem along with your attempt. If someone wants to answer then they will otherwise you will get nothing? 

We should be appreciative of the responders for their valuable time and answers.

I think, you need to apologize to @nm for your bad behaviour.  

@DSkoog 

 

Thank you for your efforts. But I am still waiting for you to follow it.

@Christopher2222 BTW, I like SE format. Any ways, If you follow the proposed site, I will really, appreciate? 

@tomleslie 

What if we are suppose to use different intervals for a, b and c. say a is in (0,1), b is in (0.1, 0.5) and c is in (1,2)

along with a small change in the expression Expr:=f(x)+b*g'(x)+c*f'(x)*g(x) #

@tomleslie 

I really appreciate your patience. You were very close. I have modified your code to make it the way I wanted. But the problem is now that I have three loops, which I assume may cause problems if I have a more complicated system.

odeExpr2.mw

@tomleslie Once you used a = b = 0.5, for solving the system and then varied it for the expression. Doesn't it effect the results?

What I am trying to say is that a and b should vary simultaneously for both the system and Expr.  

e.g.,  Expr:=(a=0.1)*f(1)+(b=0.1)*g'(1)+c*f'(1)*g(1) # at x=1: Here f(1) etc has been found for a=0.5, which should be continuously updated for each value of a and b then used in Expr subsequently. 

I think the confusion arise, becuase I used a=b=0.5 in dsolve. I was just trying to show that the system has a solution.

 

@Thomas Richard 

Thanks. 

@koreff 

Upload your maple work sheet using the up green arrow.

@umar khan 

If you meant to say that your v(r)

v:=r->((1/4*(3*(1-(R/a)^2)^.5-(1-(r/a)^2)^.5))/2);

then 

plot(exp(v(r)/2),r=0..2e6);

will give you the desired plot.

 

 

I do not see v(r). and certainly no r anywhere in your sheet.

restart
v:=(1/4*(3*(1-(R/a)^2)^.5-(1-(r/a)^2)^.5));
R:=1:a:=1:

plot(exp(v/2),r=0..2);
 

@tomleslie 

The issue was with the Digits.

For defualt digits, P(r) = 

4.449669928*10^27

Digits:=50:

6.657168...*10^(-13)

Digits:=100:

7.2427...*10^(-64)

@tomleslie 

When I use the value of `r` for which you claim that P(r)=0, I get

fsolve(rhs(sol), r = -5*10^6 .. 0, fulldigits)

evalf(subs(r=%,rhs(sol)));

4.449669928*10^27+0.*I

 

 

Like your previous post, you have repeated the mistakes.

1. There is no such thing as `refresh` instead you should use `restart`

2. You should not assign value to `Pi`. It is pre-defined in Maple with a Caps 'P'. 

Now coming to your question which is unclear. Do you want to find the boundary condition first  and then solve the system of ODE's?

@vv 

I got the book but unable to see the code for FDM. Could you please be more specific, like page number?

@vv 

The second part of my question (second question) is, Is there a more sophisticated way to implement FDM than the one i used?

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