# Tagged Questions

Questions on the symbolic (DSolve, DifferentialRoot) and numerical (NDSolve) solutions of differential equations in Mathematica.

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### What is wrong with my formulas for a mathematical model of a double pendulum? [on hold]

I wanted to create a computer simulation on Matlab, using a model for a pendulum from this study (A double pendulum model of tennis strokes. Rod Cross. Uni of Sydney, 2006) - Link I wanted to use the ...
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### How to solve time dependent pde?

I have set out to try and solve a time dependent wave equation with specific boundary conditions, but I am running into a bit of a snag. As you can see, I am trying to solve for the wave function u[t, ...
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### Interpolating functions and NDSolve

I've been working on trying to get Mathematica to solve this system for a while now, and I have a couple of questions relating to various parts of the system: Interpolating functions: As a number of ...
19 views

### lyapunov versus coupling parameter [migrated]

i need a plot of lyapunov exponent versus coupling parameter graph for lorentz system.using the matlab program i got lyapunov versus time graph using programme below function ...
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### How to solve in principle such coupled ODEs

One example for coupled ODEs from the Mathemtica help center reads ...
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### Asymptotic solution

I have an ODE V''[z] + ( (I z0^2 w)/(3 (z - z0)^2) + (2 - (4 I z0 w)/9)/(z - z0)) V'[z] + (-(12/41) I z0 w + (23 z0^2 w^2)/369)/(z - z0)^2 V[z] == 0 ...
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### Problem using ArcTan inside NDSolve

I'm messing around a bit with using "thrust segments" on a point-mass in NDSolve and have run into a strange problem to do with using ...
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### NDSolve: Improperly assigned stepsize

This is not a question which I estimate is aided in answering by providing complete code, which is excessively long. I ran an NDSolve[] at ...
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### NDSolve and piecewise functions

I'm trying to use NDSolve on a Pde for a function that is made up of several pretty complicated functions, most of which are themselves functions of an underlying piecewise function. When I try to ...
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### Substutution of Ansatz of an ODE [duplicate]

I am only beginning to learn to use Mathematica, and got stuck while trying to implement what is apparently a simple substitution rule. So I have a second order ODE in f, and I want to put in the ...
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### How to find Eigenvalues of Sturm-Liouville problem? Getting wrong Imaginary Eigenvalues

I want to find Eigenvalues of following Sturm-Liouville problem D[(2 - MA/κ[s]) q'[s], s] + W Ω^2 q[s] == 0, Where Ω^2 is the ...
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### Maximum Likelihood Approach for parameter estimation of multi response data, could you provide a tutorial? [migrated]

I was trying to fit the parameters a time dependent system coupled of ODES relate to a kinetic experiment with multi response data. example: A->B+H A+H->C+H A->D dcA(t)/dt=-k1Ca(t)-k2Ca(t)*Ch(t)-k3*Ca(...
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### NDSolve Step Size Effectively Zero

I'm trying to solve a PDE for a function of 2 variables. The most accurate parameterizations of this equation are very unwieldy and involve numerous piecewise elements, and so right now I'm trying to ...
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### NDSolve swapping between solution branches to stay positive

I have a differential equation that I wish to solve, with the requirement that my independent variable must stay positive, but do not require it to remain differentiable. My equation comes from ...
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### How can I find the eigenvalues of a Sturm-Liouville equation?

I am trying to find eigenvalues of a Sturm-Liouville equation using Mathematica10.2, but setting different precisions in ParametricNDSolve gives me different ...
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### How to index multi-dimensional vectors in NDSolve/WhenEvent?

I want to solve a system of coupled ODEs using NDSolve with WhenEvent. But I'm having a hard time trying to index the state ...
249 views

### Why Can't DSolve Find a Solution for this ODE?

I wanted to find a basis for the set of solutions of the following ODE. $$y^{''}+\frac{1}{x^2+1}y^{'}(x)+\left[-1-\frac{1}{x^2+1}\right]y(x)=0$$ But when I try to use ...
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### Need Help to solve a ordinary differential equation

I need help to find a solution to the differential equation bellow. The solution obtained with this code is a very small negative number in all the domain, and it was mathematically proved that exists ...
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### How to solve coupled diffrential equation in closed form [duplicate]

How to solve the system analytically in the interval {to,t} x''[t]==-a0*(a1 - b*z'[t])*Cos[w*t] z''[t]=-a0*b*x'[t]*Cos[w*t] This gives an error: ...
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### How to solve DSolve[y'[x] == a Sin[x], y[xo] == 0, y[x], x] [closed]

How to solve with initial value that is parameter y[xo] == 0 DSolve[y'[x] == a Sin[x], y[xo] == 0, y[x], x]
183 views

### Coupled linear time-varying system of differential equations. Analytical solution?

How to solve the system analytically in the interval {to,t} ...
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### Multiple solutions using the shooting method

I'm trying to solve the above differential equation. I'm using the shooting method, but for each initial guess a different solution appears. Which solution is correct? Is it possible to monitor the ...
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### Selection of plotted graphic (among several) within a manipulate?

I have the following code (looks big but it's quite simple): ...
123 views

### Finding Maximum Value of ElectricField in a bounded region

I have been trying to find the maximum value of the magnitude of an electric field in a bounded region. NDSolve gives the value of the potential inside the region ...
49 views

### Variable name complication with DSolve? [closed]

I'm trying to run the code: ...
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### How can I get a list of solution points from NDSolve?

I just need a list of numerical solutions for x[t], x'[t], x''[t]. While I know how to graph ...
126 views

### Ito Process paths over a Plot3D

I was wondering if its possible to draw the simulated paths of an Ito diffusion over the probability density function. Ito Process: ...
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### Manipulate with DSolve

I have defined a set of differential equations stored in sol and I'd like to plot them while being able to change the parameters. I've tried it like so: ...
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### Heat Conduction where thermal diffusivity depends on z

I'd like to know why Mathematica is not solving this problem for me. Let's imagine a body in which the thermal diffusivity varies with z (we have a cyllindrical ...
143 views

### Result interpretation of a general solution of a nonlinear differential equation

My goal is to find the general solution of the following nonlinear differential equation: $$x'(t) = e^{-t} - \sqrt{x(t)}$$ Following this guide, I've entered in the Wolfram Mathematica the following ...
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### Improve speed of RK4 algorithm for solving ODE

For anyone with interests in dynamical system, i'm trying to plot the phase space of a given hamiltonian. My code is this: ...