1
vote
1answer
22 views

Mathematica DSolve input

I'm trying to solve this differetial eqation. dy/dx=3y^(2/3). This is my input: DSolve[{y'[x] = 3 y[x]^(2/3), y[2] = 0}, y[x], x] This is my output: DSolve::deqn: "Equation or list of equations ...
3
votes
1answer
69 views

Fourier series for e^x

I'm trying to teach myself partial differential equations from Strauss' book. I have run into a very bizarre problem - I cannot figure out what is the Fourier series of e^x! And not even Google has ...
0
votes
1answer
74 views

Solving an ODE with Mathematica, using Lagrangian mechanics

Question: The velocity of light above a hot surface decreases with the height from that surface. The velocity is given by $v=v_0(\frac{1-y}{\alpha})$ where $y$ is the vertical distance above the ...
0
votes
1answer
63 views

Solving a nonlinear system of differential equations in MATLAB or Mathematica

Is it possible to solve the system $$\dot{W}=A\left(k-\frac{M}{W}\right)$$ $$\dot{M}=B\left(k-\frac{M}{W}\right)$$ with initial conditions $$W(0)=w_0$$ $$M(0)=m_0$$ in MATLAB or Mathematica? If so, ...
-1
votes
1answer
312 views

How to plot a phase portrait for this system of differential equations?

I beg your help.. I'd like the phase portrait for this system. I don't know how to use Mathematica/Matlab ... :( If anyone can make this portrait and post a print screen here, I would thank you ...
0
votes
2answers
99 views

Concerning the general solutions to linear ODEs Y'=AY when A has multiple eigenvalues

Given linear ODES Y'=AY, where Y is a column vector, A is a 6*6 square matrix. Clearly A has 6 eigenvalues, namely r1, r2, r3, r4, r5, r6. Herein we assume r5=r2, r6=r3.That is, r2 and r3 are two ...
0
votes
1answer
32 views

Why the lower limit of this integral is 1?

I solve this differential equation using Mathematica. But I don't understand the solution. Why the lower limit of this integral is 1? I run: $$\text{DSolve}\left[y'(x)+y(x)=Q(x),y(x),x\right]$$ the ...
0
votes
0answers
101 views

Plotting graph For Z versus $\rho$ by applying numerical method and explanation of nodes

I want to draw a simulation for a graph by Mathematica but confused that where I have got struck, The equation I need to plot is, $$\frac{d^2Z}{d \rho^2}+ \frac{D-1}{\rho} \frac{dZ}{d \rho}-Z + 3S^2 ...
1
vote
1answer
123 views

Solve autonomous ODE with Mathematica

I'm given a problem with the ODE y'[x]=y[x]*Sqrt[4-2y[x]] I've tried DSolve[{w'[x] == w[x]*Sqrt[4 - 2*w[x]]}, w[x], x] which gives me {{w[x] -> -2 (-1 + Tanh[1/2 (-2 x - Sqrt[2] C[1])]^2)}} but ...
0
votes
0answers
133 views

How can I show that a given system of differential equations is stiff?

I was writing a program to solve a system of equations with Runge-Kutta method, but it doesn't work well and I decided to check what Mathematica can say about it. It turns out that I have a stiff ...
1
vote
1answer
2k views

Error When Using Mathematica To Solve Differential Equation

I have a concern of why mathematica does not like/except the independent variable x. When it is used it gives the following error: In[1]:= DSolve[{2 x''[t] + ...
-1
votes
1answer
230 views

How to make Runge-Kutta for solving nonlinear ODE system in Mathematica

How to make Runge Kutta method for system of non linear equations in this Matrix form. Matrices A3, B3 and B4 are functions of matrix X3. Initial conditions are X1=X2=X3=X4=0 and system is here $$ ...
0
votes
1answer
488 views

Mathematica - How to solve for the equilibrium?

So, I used Mathematica to create a basic SIR Disease model using the following equations: ...
0
votes
2answers
189 views

Solving ODE in Mathematica

I want to solve an ODE in the form $\{y'[t] == f[y[t]], y[2] == \{1, 2, 3\}\}$ using NDSolve in Mathematica, where $f: R^3 \rightarrow R^3$ is defined as follows, ...
-1
votes
1answer
587 views

NDSolve simple matrix problem in mathematica

I have a problem with command NDSolve in mathematica. If we have simple second order differential equation, it is easy to write code in mathematica. But if we have matrix problem (for example 4 ...
1
vote
0answers
180 views

Euler method on differential equation problem

I have this problem to solve. I want to compute the inclination of a plane $\theta(t)$ at every frame of a simulation given the following rule for its angular speed of rotation $\omega(t)$ $$ ...
2
votes
1answer
1k views

A series solution of the differential equation: $\frac{d^2u(x)}{dx^2}+ u(x)^n = 0.$

Consider the differential equation $\frac{d^2u(x)}{dx^2}+ u(x)^n = 0.$ Let the solution be $u(x) = u_0(x) + p u_1(x) + p^2u_2(x) + \cdots +p^m u_m(x).$ Now we are interested in substituting the ...