Posts: 229
Threads: 24
Joined: July 26, 2017
Reputation:
2
Differential equations
June 13, 2019 at 4:58 am
So, in my university mathematics textbook, there is a series of tasks such as:
So, the variables can be separated, however, in order to solve the equation, you apparently need to solve an integral such as:
And that integral, as far as I know, can't be solved. Do you have any idea how to solve such equations?
Posts: 229
Threads: 24
Joined: July 26, 2017
Reputation:
2
RE: Differential equations
June 18, 2019 at 12:12 am
Any answers?
Posts: 19266
Threads: 176
Joined: July 31, 2012
Reputation:
92
RE: Differential equations
June 18, 2019 at 4:52 am
Just feeling stupid here...
y = x e^(dy/dx)
dy/dx = dx/dx.e^(dy/dx) + x. d^2y/dx^2.e^(dy/dx)
dy/dx = ( 1 + d^2y/dx^2) . e^(dy/dx)
Getting rid of the exponential...
y = x. dy/dx / ( 1 + d^2y/dx^2 )
Is this solvable? I don't know...
Anyway, for help on solving weird integrals, you can always refer to the old Abramowitz: http://people.math.sfu.ca/~cbm/aands/abr...stegun.pdf
Alternatively, if you're really really really lazy, there's wolfram alpha.
It says that you have a version of d'Alembert's equation in your hands.
Posts: 16073
Threads: 304
Joined: July 24, 2013
Reputation:
101
RE: Differential equations
June 18, 2019 at 5:40 am
(This post was last modified: June 18, 2019 at 5:41 am by BrianSoddingBoru4.)
Quote: Do you have any idea how to solve such equations?
Personally, I would hire a mathematician. Not sure what the going rate is, but I expect you could get one for a kebab and a bottle of beer.
Boru
'A man is accepted into a church for what he believes. He is turned out for what he knows.'  Mark Twain
Posts: 3860
Threads: 366
Joined: December 12, 2015
Reputation:
22
RE: Differential equations
June 22, 2019 at 7:53 am
(This post was last modified: June 22, 2019 at 7:53 am by Jehanne.)
(June 13, 2019 at 4:58 am)FlatAssembler Wrote: So, in my university mathematics textbook, there is a series of tasks such as:
So, the variables can be separated, however, in order to solve the equation, you apparently need to solve an integral such as:
And that integral, as far as I know, can't be solved. Do you have any idea how to solve such equations?
Matlab, Maple, Mathematica, and Derive are some software packages that you can try out.
Posts: 229
Threads: 24
Joined: July 26, 2017
Reputation:
2
RE: Differential equations
June 22, 2019 at 11:44 am
(June 22, 2019 at 7:53 am)Jehanne Wrote: (June 13, 2019 at 4:58 am)FlatAssembler Wrote: So, in my university mathematics textbook, there is a series of tasks such as:
So, the variables can be separated, however, in order to solve the equation, you apparently need to solve an integral such as:
And that integral, as far as I know, can't be solved. Do you have any idea how to solve such equations?
Matlab, Maple, Mathematica, and Derive are some software packages that you can try out.
I've tried asking Wolfram Alpha, which is, as far as I know, even more powerful than any of those things, and it doesn't give me any useful answer
Posts: 3860
Threads: 366
Joined: December 12, 2015
Reputation:
22
RE: Differential equations
June 22, 2019 at 1:10 pm
(June 22, 2019 at 11:44 am)FlatAssembler Wrote: (June 22, 2019 at 7:53 am)Jehanne Wrote: Matlab, Maple, Mathematica, and Derive are some software packages that you can try out.
I've tried asking Wolfram Alpha, which is, as far as I know, even more powerful than any of those things, and it doesn't give me any useful answer
You may be stuck with just a numerical solution; some integrals cannot be evaluated explicitly.
Posts: 23708
Threads: 1530
Joined: May 24, 2012
Reputation:
68
RE: Differential equations
June 22, 2019 at 3:57 pm
(June 13, 2019 at 4:58 am)FlatAssembler Wrote: So, in my university mathematics textbook, there is a series of tasks such as:
So, the variables can be separated, however, in order to solve the equation, you apparently need to solve an integral such as:
And that integral, as far as I know, can't be solved. Do you have any idea how to solve such equations?
Isn't that what distributes power to the axles of a vehicle?
Posts: 229
Threads: 24
Joined: July 26, 2017
Reputation:
2
RE: Differential equations
June 27, 2019 at 6:43 am
Jehanne Wrote:You may be stuck with just a numerical solution; some integrals cannot be evaluated explicitly. Well, I don't think the mathematics textbook would include series of tasks that cannot be solved.
Brian37 Wrote:Isn't that what distributes power to the axles of a vehicle? I don't know what you are talking about. You are familiar with that equation from somewhere?
Posts: 3860
Threads: 366
Joined: December 12, 2015
Reputation:
22
RE: Differential equations
June 29, 2019 at 1:14 pm
(June 27, 2019 at 6:43 am)FlatAssembler Wrote: Jehanne Wrote:You may be stuck with just a numerical solution; some integrals cannot be evaluated explicitly. Well, I don't think the mathematics textbook would include series of tasks that cannot be solved.
A numerical analysis text is full of such problems.
