Questions on the analytic and numeric equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).

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1
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0answers
105 views

Solving a set of trigonometric equations [closed]

I've been trying to solve the following equations in order to plot Subscript[θ, 41] with respect to Subscript[θ, 2] from 0 to ...
1
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1answer
64 views

Using NSolve for Elliptic Equations over Fundamental Parallelogram in Complex Plane [closed]

I'm considering solving elliptic functions over a fundamental domain of the torus with half-periods $\omega_{1}=\pi/2$ and $\omega_{2} = \pi \tau /2$, where $\tau$ is the modular parameter of the ...
0
votes
0answers
76 views

How can I solve this system?

Can anyone help me? Consider, with H > 0 ...
0
votes
1answer
44 views

Solving a trigonometric equation for all $x$ using constant coefficients

I want to find the coefficients $a$, $b$, $c$, etc. that make an equation like $a+bx=x$ true for all $x$, but for trigonometric functions of $x$. For example ...
0
votes
1answer
60 views

Shooting method — why is NDSolve giving me an error message?

I am currently trying to write a code to implement the so-called shooting method (I've given a brief description of it below, for those unfamiliar) for second order ODE's in the form ...
0
votes
1answer
57 views

How can I solve NDSolve with a parameter?

I'm a new user and I have no idea how to solve the equation with a parameter by using NDSolve. For example consider following differential equation (DE): ...
1
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2answers
130 views

Solve of cubic and quartic equations too slow

In my problem I have a third order algebraic equation for the variable sigma, all other letters are parameters. Here is it's right-hand side, left hand side is ...
2
votes
2answers
84 views

How to find variable values that make an expression divergent or undefined?

How can I find all the values of a variable at which a given expression diverges or becomes undefined? Example: expr=1/(1-x^2); Desired result: ...
0
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0answers
42 views
2
votes
2answers
74 views

Solving a linear system of symbolic variables and symbolic parameters

I am trying to run the following code to solve a system of 4 equations. ...
1
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2answers
90 views

Solve an algebraic equation

I want to obtain some positive x and y which satisfy the equation 0.01x^2-0.01x^3-0.01x+0.01x^2+y=0 I have written: ...
0
votes
1answer
74 views

Solve doesn't give me all the solutions I expect

I have a problem with Mathematica 10, and I really don't know what's happening here. I try to plot some orbitals and then solve a simple equation. But Nathematica only gives me one the solution, ...
2
votes
1answer
126 views

How do I make Mathematica show me the solutions that it has found while it is searching for them

How do I make Mathematica show me the solutions that it has found while it is searching for them, specifically in this: ...
0
votes
1answer
47 views

Output of Coefficientrules into Jacobian matrix

I have a pair of large polynomials in u, v, a1...a9 and b1...b9, generated by ...
0
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0answers
79 views

Speed up the Eliminate

I have problem of eliminating some variables from a set of equations, which contain logarithmic function, in order to obtain a differential equation. These are the parameter and functions in ...
-1
votes
1answer
55 views

Solve Numerical Equation [closed]

I want to find $x\in \ \mathbb{Q} $ such that the first ten digits of $ x \pi $ are 1.234567890. I tried: ...
1
vote
3answers
126 views

Find all solutions which satisfy the given conditions

Let $$ m=9n^3+30n^2-9n $$ where $n \in \mathbb{Q^{+}}$ and $m \in \mathbb{Z} $ . Find all solutions which satisfy the given conditions. So I've tried to solve this manually and I was ...
1
vote
1answer
103 views

Wrong root when using numerical values

I have the following inequality: $$ \sqrt{\frac{a}{2x}}+ \frac{b}{1-\frac{a}{a+\sqrt{a(2bx + a)}}} + \frac{a}{2x\frac{a}{a+\sqrt{a(2bx + a)}}\left(1-\frac{a}{a+\sqrt{a(2bx + a)}}\right)} < f $$ on ...
2
votes
3answers
445 views

Solving an equation involving an integral

How do I get the following into Mathematica, solving for $a$: $$ 0.7 = 1 - \frac{2}{a} \times \left[ \frac{1}{a} \int_0^a \frac{x}{\exp(x)-1}\mathrm dx + \frac{a}{6} - 1\right] $$
1
vote
1answer
69 views

Improving strategy to solve this constrained root-finding problem

I am looking for roots of the function eqs defined below. It has $2k$ unknowns and returns a vector of $2k-1$ components. The sole purpose of the following block ...
0
votes
0answers
28 views

Solve involving simple cancellation on both sides fails when there are too many constants

I've been working with a number of equations of the form x = A * B * x ^ C where I need to solve for x--basically, equations ...
0
votes
1answer
164 views

Nonrectangular tensor encountered [closed]

I am trying to solve a system of equations which characteristic matrix: ...
0
votes
0answers
40 views

Probleme with Ted Ersek's RootSearch package [duplicate]

The following question is a logical continuation of this one. The Ted Ersek's RootSearch package doesn't work with this code: ...
0
votes
3answers
129 views

Manipulation linear systems of equations

I have the following system of equations: i1 = ix - β*ib; i2 = (β + 1)*ib; i3 = ix + ib; vx = i1*Rc + i3*Rb; v1 = i2*Rϵ + i3*Rb; v1 = -ib*rπ; I tried using: ...
2
votes
0answers
91 views

Solving this system of nonlinear equations

Edit Interestingly, I realized solving my problem with $2n$ equations appeared to be more efficient than using mathematical results on the solutions to reduce the problem to $n$ equations (the $n$ ...
1
vote
1answer
92 views

Help with findroot optimization

I'm trying to solve the set of coupled equations $$\frac{-N -2( \lambda + N(\frac{\beta}{\epsilon}-\lambda))\upsilon_l + N ...
3
votes
2answers
118 views

Show Factorial instead of Gamma in the result of RSolve

Now I wanted to solve for a recurring function with RSolve. Here's how I tried: ...
3
votes
0answers
140 views

Complex boundary conditions and NDEigensystem

I am having difficulties implementing a Neumann value when numerically solving the Navier equation using NDEigensystem. The Navier equation is given by $\nabla^2 \vec u + (p^2 - 1) ...
0
votes
1answer
73 views

Invert and fit implicitly defined curve

I need to fit an implicitly defined curve. I thought I could get some data out of Solve, and then using FindFit. Therefore, I ...
-2
votes
1answer
62 views

How to solve this non-linear equation? [closed]

b=12 a=2.787 solve[b/x-((1-(a*(((b x)/(b+2 x))^(4/3))))^(-2/3))- ((1+(a*(((b x)/(b+2 x))^(4/3))))^(-2/3))==0,x] I gave the above code and the output came ...
1
vote
1answer
57 views

Mathematica cannot find intersection of two functions [closed]

Why mathematica cannot solve this extremely easy equation? [![My functions][1]][1] g[x_] := -x + 2 h[x_] := 3 x f[x_] := -x^2 + 4 http: // ...
2
votes
1answer
120 views

How to put the result of NDSolve in a function?

I have solved an ODE with NDSolve, and put the result in S: S = NDSolve[{y'[x]==(y[x]^4+y[x]+1)^(1/2),y[0]==0}, y, {x, 0, 100}] But i don't want to plot y[x] ...
4
votes
1answer
115 views

How do I solve a system of equations for only one variable quickly?

I have four order-2 polynomial equations in four unknowns. Call the unknowns x1,x2,x3,...
0
votes
3answers
105 views

Solving cubic equation with unknown coefficients

I am trying to solve a cubic equation with unknown coefficients (p and t), here is the code: ...
1
vote
2answers
85 views

Solving an equation of one parameter over a range of values of that parameter [closed]

How can I use NSolve the following situation (to rectify a cycloid arc mapping with hashes etc.)? For a specific value on the right-hand side, I use ...
1
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4answers
158 views

Find zeros of a transcendental function

Mathematica 10 can not give me solution of this equation ...
0
votes
1answer
72 views

How to solve a linear system inside Manipulate and use the result for Plot?

I typed a code for showing a plane and a line, and solve a system, but I can´t show the intersection, because I don´t know. Here is a minimal working example for understanding my problem ( the real ...
0
votes
1answer
72 views

Implementing AiryAiPrimeZero function

There are some functions implemented in the Wolfram Language related to Airy functions. For example, AiryAi, AiryAiZero or ...
1
vote
3answers
154 views

Find zeros of function in 2 variables

I have two functions $f(r,\phi)$, and $g(r,\phi)$. What is the best way to find the curve in the plane $(x,y)$ or $(r,\phi)$, over which $f(r,\phi)=g(r,\phi)$? I know how to plot it, using ...
4
votes
3answers
98 views

How can I stop Solve returning the value of a root encapsulated in a list?

I have a Solve similar to the following: ...
2
votes
0answers
49 views

Why doesn't RSolve work here? [closed]

RSolve[ {θ[n + 1] == θ[n] + 0.25*ϕ[n], ϕ[n + 1] == ϕ[n] - 2.5*Sin[θ[n]], θ[0] == π/2, ϕ[0] == 0}, {θ[n], ϕ[n]}, n] What's wrong with my code? I know ...
1
vote
1answer
61 views

FindRoot::Istol error

I recently tried to find a root with FindRoot in Mathematica. I know that the problem has a solution, but when using FindRoot, this error appears : ...
1
vote
0answers
64 views

Why FindRoot fail in this case?

I'm trying to solve a set of equations: $$\frac{\epsilon+(k(1-N)+2\beta)\upsilon_l-\epsilon \upsilon_l^2-2\Omega(1-N)\upsilon_l^3}{-\Omega\upsilon_l^4+k\upsilon_l^2-\Omega}=\sum_{j\neq ...
1
vote
1answer
59 views

Assigning solutions to a variable [duplicate]

If I do Solve[x+1==0, x] then I get {{x -> -1}} But I want to assign the solution -1 directly before seeing the result, ...
0
votes
0answers
54 views

FindRoot for vectors

My problem is the following: quad = 26; R is a quad x 3 matrix, lpand ...
0
votes
1answer
123 views

Conditions for real roots of a cubic polynomial with complicated, yet constant, parameter values

Can anyone find conditions on the following parameters $\sigma_{\ell}$, $\mu_{\ell}$, $d_{\ell}$ and $\sigma_M$ such that the cubic: $$ (d_{\ell}-d_{\ell}\sigma_M)\ell^3 + ...
1
vote
0answers
84 views

Solve works with numbers, but not with free variables [closed]

The following code prints the correct solution for variable a (2.23). But if I comment out the five assignments given at the top, the code fails. When I remove ...
1
vote
1answer
71 views

Solving a differential equation with a specified “input vector”

I have the following differential equation: ...
1
vote
0answers
78 views

Solving a tensor equation in xTensor [closed]

I want to solve the following equation $\frac{1}{4} R_{ab} g_{cd} - \frac{1}{2} g_{ab} R_{cd} + 4 R_{ab} g^{ef} \nabla_e \nabla_f R_{cd} + 2 g_{ab} R_{cd} g^{ih} g^{ef} \nabla_e \nabla_f R_{ih} = ...