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1
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3answers
68 views

DSolve with assumptions

I'm new to mathematica and was wondering if someone could help me. I have a differential equation which is: $\frac{dy}{dx} = 1/2 y(1 - y)(a - y + a y)$ It has initial condition $y(0) = y0$ and ...
1
vote
1answer
40 views

Plotting 2nd order ODE solution for specific values of constants

Suppose that I have a 2nd order, linear ODE and I want to plot the solution I found using DSolve. How can I plot giving specific values of ...
0
votes
1answer
37 views

Problems with DSolve [closed]

I'm trying to solve and plot a second order ODE. Here is my code: DSolve[y''[x] + 4 y'[x] + 12 y[x] == 80 Sin[2 x], y[x], x] Problem 1... it sticks me with a ...
0
votes
0answers
66 views

DSolve response with DSolve

I'm trying this code ...
0
votes
1answer
60 views

Using WhenEvent

I want to solve this simple equation with a event: ...
1
vote
1answer
86 views

Solving ODES in order to find unknown constants

I am trying to solve a set of ODES which represent a second order consecutive chemical reaction. ...
1
vote
1answer
105 views

Forcing solutions to avoid Root[]

I'm solving a system of ordinary non-homogeneous differential equations (4 equations). The solutions will include some algebraic equations solutions as known from text books due to the use of an eigen ...
0
votes
1answer
109 views

Problem adding boundary condition using DSolve [closed]

Here is my code: ...
0
votes
1answer
73 views
0
votes
0answers
27 views

Substitution employed to DSolve [duplicate]

How do we get Mathematica to express generally what substitution has been employed in obtaining DSolve outputs? e.g.for solving particular: $ \int \sqrt {\sin^{-1} {\sqrt x }}dx $ EDIT1: ...
0
votes
1answer
25 views

Defining a function then using it in DSolve

Probably a pretty simple question but I've been stumped for awhile looking around. I'm trying to solve four diff. eq.'s using DSolve and some of these equations depend on a function B[t] which I try ...
6
votes
1answer
107 views

DSolve giving strange error messages solving a PDE

Consider this set of PDE $$\left( x^{2}+y^{2}\right) \dfrac {\partial u}{\partial x}+n x y\dfrac{\partial u}{\partial y}=0$$ have general solution $$u\left( x,y\right) =f\left( \dfrac {1}{n-1}\dfrac ...
3
votes
1answer
83 views

How to deal with the discontiuity in the solution of NDSolve?

I have a set of differential equations that describe the air temperature dynamics in a heated channel.The problem is that the solution becomes unstable and creates a discontinuity but physically it ...
1
vote
1answer
125 views

error DSolve::dsfun: cannot be used as a function

I tried to solve system of ODEs, but something was wrong. ...
0
votes
0answers
62 views

NDSOlve - 1D wave equation with boundary

I am currently trying to solve the 1D wave equation with Mathematica: $$c^2\frac{\partial u}{\partial x^2}=\frac{\partial u}{\partial t^2}$$ I want to do so for a cantilever with a tip mass: One ...
0
votes
0answers
17 views

Why does the assignment of values to coefficients make a difference to the completion time of DSolve?

I hope to solve the following DAE equations using DSolve, (simplified example, may not be solvable): ...
0
votes
0answers
21 views

Solving an inhomogeneous partial differential equation [duplicate]

Here is my inhomogeneous partial differential equation: $$ \left ( \frac{\partial^2 }{\partial \rho^2}-\frac{1}{\rho} \frac{\partial }{\partial \rho} + \frac{\partial^2 }{\partial z^2}\right ) \psi= ...
2
votes
2answers
110 views

Overdetermined System of PDEs

EDIT: Just to clarify a large part of my question is whether there is a way to make Mathematica solve a system with more equations than independent variables (so a system that is overdetermined but ...
1
vote
1answer
81 views

How to impose normalization condition (not initial condition) on DSolve or NDSolve?

I have a set of differential equations (or DAEs): $\begin{cases} 5x_{2} + 3x_{4} + 3x_{5} = \frac{dx_{1}}{dt}\\ 5x_{1} + 5x_{2} + 5x_{3} + 3x_{4} + x_{5}= 0\\ 3x_{2} + 3x_{4} + 10x_{5} = ...
1
vote
1answer
33 views

DSolve with Absolute Value

When playing around with DSolve, I enter the following: DSolve[{Derivative[1][y][x] == x + Abs[x]*y[x]}, y[x], x] The output is: $$y(x)\to e^{\frac{1}{2} (x ...
0
votes
1answer
76 views

Method that combine LinearSolve and Dsolve for a set of differential equations?

I have a matrix for example: $\begin{bmatrix} 0 & 5 & 0 & 3 & 3\\ 5 & 5 & 5 & 3 & 1\\ 0 & 3 & 0 & 3 & 10\\ 1 & 3 & 2 & 3 & 10 \\ 1 ...
1
vote
1answer
73 views

System of differential equation with delay

I try to solve this differential system with delay: ...
0
votes
2answers
113 views

Lotka Volterra Equation Plotting

So I have a basic Mathematica assignment where we need to numerically solve a Lotka-Volterra predator-prey population equation. So far I have managed to come up with this ...
0
votes
0answers
46 views

DSolve gives back input (coupled ODEs)

I'm trying to solve a system of coupled ODEs, however I keep getting back the input whenever I try to solve with DSolve. The variables I'm solving for are complex. Here's what I have : ...
1
vote
1answer
68 views

DSolve for Second Order Differential

I have an equation y''[t] + w^2*Sin[y[t]] == 0 So I'm using DSolve like this: ...
0
votes
1answer
47 views

EllipticF reduction

Is it possible to reduce the following Z to Legendre form Elliptic integral of the First kind? $$ \int \dfrac {\sec u\; du } {\sqrt{ (1- {(\nu \tan u)}^2 }} ..(1*)$$ With ...
0
votes
0answers
105 views

Issue in NDSolve and unknown error

I try to solve a simple BVP: $A {v}''(t)+B v(t)=f(t)$ where $A, B$ — $5\times 5$ matrices, $f(t)$ — 5-dimentional vector-function with the use of NDSolve. Each component of $f(t)$ is a combination ...
1
vote
1answer
75 views

Strange constants in a PDE solution by DSolve

I'm solving the following PDE: DSolve[F''[ξ] + (Ω^2 - M^2 Exp[2 α ξ]) F[ξ] == 0, F[ξ], ξ] And Mathematica gives a general solution in terms of modified Bessel ...
1
vote
0answers
171 views

NDSolve: Equation with interpolating function [closed]

I have a question regarding DSolve and NDSolve functions in Mathematica 10. For instance, I'd like to solve an ODE: ...
0
votes
1answer
89 views

Parametric Plotting

I am trying to make a parametric plot of the x and y displacements of a vibration problem. When trying to plot the parametric curve won't show up.
0
votes
0answers
59 views

when DSolve fails

I am doing this mathematical problem $c*G_{vv}+ d*G_{u} + e*G_{v} +f*G=0$, where $c, d, e$ and $f$- are constant coefficients. I already know that this is second order PDE and we classify it by ...
4
votes
1answer
239 views

How to solve this Integral equation

D[x[t] - x[t - 1]/(2 E), {t, 3}] + Integrate[E^(-δ)*x[t - δ]/5^t, {δ, 2, 2.5}] == 0 I found solve this problem is hard with Mathematica. I also find a article ...
0
votes
1answer
56 views

DSolve for first order nonlinear equation is solution numerical or analytical?

Hi I'm new to mathematica so I may have a somewhat trivial question. my code below solves and plots the results of a first order nonlinear ODE. The solutions mathematica gives me contains & and #1 ...
1
vote
0answers
105 views

Why is my output equal to my input?

I tried to solve a system of differential equations with the code below: ...
1
vote
2answers
135 views

DSolve bvlim error due to Boundary condition at infinity

I am solving an Ode using Mathematica that has boundary condition at infinity which is why Mathematica is showing error message. Please help to tackle this problem. ...
0
votes
0answers
127 views

DSolve echoes input

I'm attempting to solve a set of coupled, non-linear ordinary differential equations using DSolve, but Mathematica simply echoes the code that I put in: ...
1
vote
1answer
78 views

Fit to inverse function

I am trying to fit my data to an inverse function from solving a DGL: ...
0
votes
1answer
56 views

Why does DSolve fail here?

I have the following differential equation: a*L'[t] == 40000*L[t]^(-3/2) - 1.4 - extf I want to fit the solution to data in order to acquire a. I tried DSolve ...
0
votes
1answer
88 views

Problem with DSolve [closed]

I am trying to use DSolve: DSolve[{y'[x] == x/y, y'[8] == 2}, y[x], x] But I get an error message: DSolve::dvnoarg: The ...
5
votes
0answers
147 views

Second order differential equation with boundary conditions solving repeatedly

I want to solve a second order differential equation in the interval[-1:1], which does not have a analytic solution, \begin{eqnarray} y''(x) &=& k \phi^2(x)y(x) \\ \phi(x) &=& ...
0
votes
0answers
128 views

How to solve system of non linear Differential Equations with 1 independent variable and 3 dependent variables?

I have been trying to solve this system of differential equations using mathematica. $$F(t) B''(t)+B'(t) F'(t)+B(t) F''(t)=0,\\ F(t) A''(t)+A'(t) F'(t)+A(t) F''(t)=0, \\ B(t) A'(t)+A(t) B'(t)=0$$ Here ...
0
votes
1answer
71 views

How to evaluate a “pure function”? [closed]

I need to evaluate the result of DSolve, e.g. {{y -> Function[{x}, x^2 - x^3]}} at some specific point. I tried y[1] and y /. x -> 1. Hope someone knows how to do it
0
votes
0answers
60 views

Boundary condition is not specified on a single edge of the boundary of the computational domain

When I want to solve this PDE I get this error "NDSolve::bcedge: "Boundary condition u[0,0.05]==0 is not specified on a single edge of the boundary of the computational domain"" ...
7
votes
2answers
194 views

Solving with DSolve recursively

I need to find $f(x,n)$ in the interval [0,1] defined by recursion, \begin{equation} \frac{d f(x,n+1)}{dx} = f(x,n) \end{equation} with boundary conditions $f(0,n+1) = 1$ and $f(x,0)=1+ x $ Using ...
4
votes
2answers
64 views

DSolve results not what expected

I have the following formula: s'[t] == 230.94 Tan[0.914743 - 0.138564 t] When I solve this by hand I get: ...
0
votes
1answer
82 views

DSolve not returning “trivial” solutions [duplicate]

When I enter this DSolve[y'[x]^2 + y[x]^2 == 1, y[x], x] the answer I get is ...
0
votes
2answers
78 views

Solve simple differential equation - Error?

I get the error "The function Te appears with no arguments." when running this code. I'm not sure why. Is it because of the $Abs[\Gamma]$ ? ...
0
votes
1answer
133 views

Problem with NDSolve [closed]

I'm solving a PDE that is partially elliptic. So I need to solve the equation iteratively. My problem is at the end of the code. I'm doing interactions manually in order to evaluate the code. At the ...