**3.281 equation-solving questions.**

Trying to solve a coupled differential equations of motion. When there is no Working Precision mention it runs and give following plot for θ[t] but this is wrong, θ must be symmetric about 0.
...

I want solve a system with $n$ equations of motion of the first order. In these equations of motion there are creation and annihilation operators of Dirac fermions. I cannot figure out how to describe ...

Given a linear time-invariant system:
$$x'(t)=Ax(t)+Bu(t)$$
with initial state $x(0)=x0$ and final state $x(T)=xT$.
The performance measure to be minimized is:
$$∫_0^Tu(t)^2dt$$
The most important ...

Given 4 points as points = {{0, 4}, {1, 0}, {2, -1}, {3, 0}};. I want to find the coefficients of ...

I have solved the following system non-linear:
...

I try to solve a system of differential equation by shooting method. I looked at questions asked on the site but I could not find that could help me.
My functions are ;
...

I want to analytical Solve or numerical solve by Mathematica a biharmonic equation with homogeneous boundary conditions homogeneous?
I considered its solution using Fourier analysis, which is not ...

Following this and this questions, I am trying to solve Navier–Stokes continuum equations in cylindrical form for a axisymmetric, compressible and vicious flow using power series. Consider the ...

Consider an equation $(x-1)^2/25+(y+2)^2/9=1$. (x-1)^2/25+(y+2)^2/9==1How can one print all the integer points on and inside the graph of the equation?
I ...

UPDATE: The answers given are informative, and provide a workaround which has been given in other posts, but is unfortunately not very efficient. There still seems to be a lack of deeper understanding ...

I'm trying to solve the coupled differential equations:
...

This question contained the problem of NullSpace, but previous ones not.
This is a problem seems like my previous one, but there is some details different. I find that perhaps one method can not ...

This is a continuation question to Sums as rational vector dot products with a basis constants vector.
Consider the following FindInstance query. Looks easy, doesn'...

Im trying to solve a nonlinear ODE with boundary conditions, the simplified problem reads for example
$$ k \frac{\mathrm d^2 T}{\mathrm d x^2} = T^4\, , \quad x \in[0,\, 1]\, , \\
T(0)=0.9\,,\quad T(1)...

How does Mathematica solve a system of degree two polynomial equations?
I am running code that yields {} (no solutions), but I would like to replicate the manipulations by-hand.
Another concern: my ...

To an earlier problem, @Rhermans provided the following solution:
...

I want to solve the next differential equation,fun = t^2*x''[t] + 4/3*t*x'[t] - 2/3*(1 - (L^2)/(6*t^(2/3))) x[t] - (2*L^2)/(45*t^(2/3)) == 0
DSolve[fun, x, t]...

I have the following code that includes Assuming to cut through irrelevant detail, or so I had hoped.
...

The conditions in x ∉ Integers && y ∈ Integers && y == -(1/2) + x/2 are inconsistent but Reduce does not solve ...

This question is a continuation to one answered by kglr here.
In the following situation, I find that given my assumptions, it is indeed possible for $g$ to be negative.
...

I'm working with a trigonometric function, so I thought it would be convenient to set a condition to restrict the domain so I wouldn't have to specify it in the solve function each time. Here is a ...

Let's use the simple effective potential of the classical restricted three-body problem
...

I'm trying to solve a simple maximization problem, which I can easily solve by hand using the Lagrangian method.
I want to maximize UH subject to ...

where f(vt)=sin(v t); T_{1} (0)=1;T_{2}(0)=0;\Phi(m,k)=constant

I am attempting to set up a Neumann boundary condition for a PDE that evaluates differently for different times. I am using Piecewise to do this. Here is the Boundary condition:
$$U^{3/2}[x=L,t] = -\...

I'm trying to plot this function: f[x_, c_] :=
527.5658823401758`*(1 - Erf[(2 x - 1)/(2^1.5)]) +
400.6284776272996`*(Erf[(2 (-c) + 1)/(2^1.5)] + 1)I ...

I have an equation which is solved by Solve[].
When I define the variables with real numbers, I get an exact solution. However, when I'm trying to use the symbolic expression for the solution, I ...

t is a generated matrix with a parameter kz. Through solving Det[t]==0, the solutions, i.e. kz, are obtained. When I substitute any one solution in Det[t], the result is a large number, why? How to ...

I have 2 functions that look like this:
F[t_,d_]:= 10+t+2d
G[t_,d_]:= 5+t+d
I'd like to solve this in such a way to know for which t both Function have the Same value.
I assume that this won't be ...

I am trying to convert a trigonometric expression likesinθ/(1 - cosθ)intocosecθ + cotθor
...

How can I know if $(-2 + a (1 + i))/(a - 1), a=(-2 i (z - 1))/((z - i) (1 + i))$ is equal to $(1+i)(1-z)$?
I tried FullSimplify$[(-2 + a (1 + i))/(a - 1)]$ and I got $-(2 (1 + i) (i (-2 + z) + z))/(i ...

Let's say we have the following relation between different variables:
...

I have a Delay Differential Equation as given below
...

The previous question is irrelevant to the solution of tx==0, and thus is obviously different with the present one.
t is a generated matrix with a parameter kz. Through solving Det[t]==0, the ...

This is a different question with pevious one although they seems like the same. In that question m=1, the matrix t is not a complex matrix, when I change Kh as Kh=Rationalize[0.211,0], the problem is ...

Unless I misunderstood something, this is different from a similarly worded question because I am not asking for the relationship between different variables here.
I want to convert an expression ...

Consider the following equations:W*BP == X*PC
Y*AQ == Z*BQ
AC^2 == AB^2 + BC^2
PQ^2 == BP^2 + BQ^2
AP^2 == AB^2 + BP^2
BC == BP + PC
AB == AQ + BQLet's say, I ...

Take for example the equation
$$
n^2=x^2+y^2+1
$$
where $x,y$ are integers.
This equation admits solutions only for some values of $n$, to wit,
$$
n=1,3,9,17,19,33,35,51,73,81,99,\dots
$$
Can we ...

Short version: Do the methods (or other things the function uses to solve the equations like time steps or error estimates) that NDSolveValue uses by default depend on the types and quantity of ...

How to calculate $\frac{d\phi}{dz}$ from following equation:
$$A\frac{d^2\phi}{dz^2}+\cos(\phi)\sin(\phi)=0,$$ where $A$ is a constant?

I have some singular transition rate matrices $m$ (columns add to zero). They have exactly one zero eigenvalue that I want to find the corresponding eigenvector of (the rest of the eigenvalues are ...

I want to solve a system of partial differential equation in mathematica.
equation is:
$y0=0.5 t0=30 λ_12=0.3 λ_13=λ_23=0.01 λ_21=2.8$
I am new in mathematica. please help me for solving ...

Mathematica 11.3.
I am not sure if this solution given by Mathematica is correct. But I'd like to ask the experts.
...

I would like to solve this equation:
$$-x\sin(x)=\cos(x)$$
But Solve in Mathematica doesn't work:
This system cannot be solved with the methods available to <...

I am solving Laplace equation on circular domain from which i get solution for potential.
The code I used:
...

I wrote the following code:Solve[{x == VIN/VOUT, VOUT == 5 VIN}, {x}]Mathematica does not solve it. How can I get the result x=1/5?
Thank you so much for your ...

I am given $48 \times 48$ matrix $A$ and a vector $b$ and I would like to solve system $Ax = b$. I know that $A$ is underdetermined, i.e. there exist many solutions for $x$. Due to some considerations,...

- differential-equations
- plotting
- numerics
- numerical-integration
- polynomials
- functions
- linear-algebra
- calculus-and-analysis
- simplifying-expressions
- mathematical-optimization
- matrix
- nonlinear
- symbolic
- special-functions
- list-manipulation
- complex
- performance-tuning
- error
- parametric-functions
- trigonometry
- inequalities
- recursion
- function-construction
- programming
- difference-equations

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