# Questions tagged [equation-solving]

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

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### Is it possible to use FindRoot with a function of two variables? [closed]

How can I use FindRoot with 2 variables function? Is there a different way to do that? For example ...
36 views

### Conditions to make unitary a given matrix

Suppose I have some symmetric matrix W = {{c[1, 1], c[1, 2], c[1, 3]}, {c[1, 2], c[2, 2],c[2, 3]}, {c[1, 3], c[2, 3], c[3, 3]}}; where the c's are complex and I ...
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### Finding closed forms for various addition laws on elliptic curves, FullSimplify fails even with assumptions?

I would like to get Mathematica to do some tedious algebra for me, but I have been unsuccessful so far, and I don't know whether I am not using it correctly or whether it is simply not sophisticated ...
172 views

66 views

### Problems with manipulation

I am plotting geodesics on an ellipsoid. My problem is that I cannot do the manipulation, from a, b, c. From the starting point and the initial vector, the manipulation works well, but from the ...
65 views

### ListPlot3D of the results of FindRoot

I have a system of 2 simultaneous equations where i want to calculate the values of Tc and Tc which ranging with the values of two variables which are wfc and V. I tried to evaluate it by using ...
67 views

### Limiting solution space for symbolic algebra problems

I have a system of 12 quadratic equations with 12 variables (x11, x12, x21, x22, x23, x33, p1, p2, p3, ϕ, μ, τ) and several positive constants,w, q1, q2. ... > 0<...
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### Vortex motion equation for flux-flow instability

I am solving the motion equation of an isolated vortex oscillation in a superconductor. I am assuming that the driving force is generated by an RF current oscillating at 1.3 GHz. The main point of ...
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My code is ...
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### Error messages for FindRoot and NIntegrate

I want to solve the following problem. First, the setup. A function $V(\varphi)$ defined as \begin{multline} V(\varphi)=\frac{\alpha-3}{4}e^{\sqrt{2\alpha}\varphi}+\frac{\alpha-5} {\gamma}e^{(\...
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### NSolve cannot find solution to system of trig equations

I was making a program to convert a rotation matrix to a set of euler angles. I wanted to do this for any valid rotation order that the euler angles were made with, and I did not want to do it the ...
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### Five equations to solve 6-variables question, is it possible?

I was given a task to find the value of variable a,b,c,d,e and f. But I'm not sure it is even possible, given that only 5 equations are available. Can anybody point out how to solve these: ...
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### Still having problem with solving high polynomials with exponential equations simultaneously

I need to find the value of Ta and Tc for two simultaneous equations to get a numerical answer using NSolve. I have tried using FindMinimum and NMinimize and still could not solve the problem. Here is ...
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### Why does Mathematica just return Hold of my Input? [closed]

Example: Solve[x^2 + a x + 1 == 0, x] Output: Hold[Solve[x^2 + a x + 1 == 0, x]] What is the problem? Any child can solve this in its head
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### Solving BPV of second order nonlinear ODE through NDSolve

I'm trying to solve a 2nd order related ODE system in two region using Piecewise. BC: 1) y'=0 and at y'[1.6]=0 while at 1 <...
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### Has Mathematica 12 gotten worse at solving simple equations?

Mathematica used to be easily able to solve an equation like this: Reduce[Log[Sqrt[k p]/Log[k]] == 0, p] (I can easily do it myself, at least I can find the ...
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### Triggering WhenEvent as a result of WhenEvent

I'm attempting to solve a dead-simple differential equation with events: ...
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### Discontinuity in plotting the solution of a trig function system

I have the following system ...
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### Solving equations, checking linear dependency of equations

I have the following input and try to do solve the equations for in total four unknowns. When I run the input only "solutions" for two of the four unknowns are given in the output. I am not quite sure,...
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### Can not solve this question [closed]

Solve[beta*x *((1 + (1 - m)*sigma*theta ((x^(-1/2) - 1)/((1 - theta)*x^(-1/2) + theta)))) - S == 0, x] Can someone please help me, I don't know why x is not ...
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### How do I plot the output of Solve as a function? [closed]

I have a system of equations (13 eq) and I want to solve for S. There are four solutions in terms of k and ...
111 views

### Tangent point coordinates when the curve is a set of points

I want to find the coordinates of the tangent point between a convex curve and a line that passes from a point with known coordinates (0,b) ("efficient portfolio" ...
66 views

### Help with solving a PDE and plotting its solution

I have trouble with solving the PDE with periodic boundary condition, which appears to be stiff somewhere, so I tried "StiffnessSwitching". But the code still doesn'...
31 views

### Plotting roots of a non polynomial function

I'd like to plot the solutions of a function f(y)=k, when f(y) is non polynomial. This is the Mathematica script I have produced so far: ...
58 views