Tagged Questions

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

102 views

Disease Network Model Using NDSolve

I have a basic disease model using NDSolve: ...
116 views

Series expansion of NDSolve solution produced by shooting method

The ODE I need to solve is ...
47 views

Two identical expressions for ODE, two distinct result

I have a problem in solving ODEs: two identical expression provides me different answers! I have no idea what's going on, can any one give me some reason why the following two expressions are ...
60 views

Simplify huge output or using the output without showing it in full [closed]

I'm trying to solve a system of differential equations. It works fine but Mathematica creates a huge output, which, when shown in full, results in a file size about 100 mb. Using Simplify doesn't work ...
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: ...
89 views

Finding roots by solving its ODEs [duplicate]

Roots of fluctuating function (p,q real) needed to evaluate eigenvalues of $$y(x) = \dfrac{\sin px }{p} + \dfrac {\sin q x }{q} =0 ...(1*)$$ form a real and complex infinite set. The way to ...
41 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 ...
320 views

Find the eigenvalues for an ODE

For example, say I have $y'' + \lambda y = 0$ and the endpoint conditions are $y'(0) = 0$ and $y'(\pi) = 0$. How can I find the values for $\lambda$ that for which there is a non-trivial ($y\neq0$) ...
200 views

NDSolve: basic settings for PDEs

I am trying to learn how to solve PDEs in Mathematica in order to deal with relatively simple problems without needing to formulate weak formulations in FreeFem++, which is rather time consuming for ...
109 views

Using manipulate with a defined funtion to solve a ODE

As many in this community I'm new in Mathematica and while exploring the numerical solver for differential equations, I tried: ...
181 views

How can I make a 3D Plot with NDSolve?

I have a system of coupled ODEs which I am solving using Mathematica. I am solving these using NDSolve: ...
521 views

Click in a vector plot to plot several solutions of a system of differential equations

I am aware of the Locator button and I am aware of the Equation Trekker package, but they are not what I want to use. Here is what I specifically want to know how to do, if possible. Consider the ...
148 views

Delay difference equation

How can I correctly specify and solve a system of delay difference equations in mathematica similar to NDSolve with regard to delay differential equations? For example if I want to "see" the values ...
186 views

Using parts of piecewise function

I define: f[x_] := Piecewise[{{5, 0 <= x < 10}, {g[x], 10 <= x < 15}, {h[x], x > 15}}] Then I try to solve ODE: ...
487 views

solving PDE with periodic boundary conditions

I want to solve a 2D-PDE that has the form ...
464 views

How to solve Laplace equation in 3D?

Basically I want to solve Laplace equation for truncated octahedron in a cube matrix. The boundary condition is Concentration u=200 at surface of truncated octahedron and u=15 at boundary of cube. I ...
210 views

DSolve giving strange error messages solving a PDE

Bug introduced in 6.0 or earlier and fixed in 10.1 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 ...
230 views

Implicit differentiation and the Folium of Descartes [duplicate]

Given the function (Folium of Descartes) $x^3 + y^3 = 3xy$, how would I find the equations for tangent and normal lines at the point $\left( \frac{3}{2},\frac{3}{2} \right)$? I know that I must use ...
140 views

Phase Portrait Trajectories

How do I make a phase portrait which looks like the ones demonnstrated here? Not the fancy version where I can use the controls to change it, just a screen-shotted version of say a spiral point? Any ...
134 views

Using InterpolatingFunction in equations

I tried to use InterpolatingFunction in another ODE, but it doesn't work, because it seems for Mathematica that 2 functions are unknown instead of one. ...
40 views

DSolve of the system of two equations with known constants

In my previous post DSolve solution of two unknowns we conclude that Math 10 obtained results fast and that Math 9 did not give the solutions at all after one day. Now I have a problem if there are ...
138 views

System of Partial differential equations

I am trying to solve numerically a system of 3 partial differential equations and I am facing a problem. My functions are f[x,t], ...
I have the equation $y'' + 16y' + 64y = 0$ Repeated root of aux eqn $r = -8$ Given the initial conditions, how do I solve for the constants $A$ and $B$? ...