# Tagged Questions

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

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I'm rather new to mathematica. I'm attempting to express: $$\sqrt{x} = \frac{\gamma \sqrt{y}}{-i(\Delta - g \sqrt{1 - (\frac{\tau}{4lhx})^2})+\frac{\gamma}{2}}$$ as $$0 = Ax^4 + Bx^3 + Cx^2 + Dx + E,... 1answer 92 views ### Passing starting values to FindRoot when called by the Shooting Method of NDSolve According to the documentation of the NDSolve Method -> "Shooting" option, it is possible to pass to ... 0answers 67 views ### How to systematically approach when solving a large system of differential equations? I defined several functions in order to get to the final system of a partial differential equations I have to solve. Here is how I did those definitions: ... 1answer 36 views ### “Solve” with problem “Solve::ivar: ”-1+t is not a valid variable.“” Solve[{Ee1*ek1 + g*h*(1 + r) + j1*h*ek2 == ek1, Ee2*ek2 + j1*h*ek1 + j2*h*ek3 == ek2, Ee3*ek3 + j2*h*ek2 == ek3}, {r}] want to get ... 0answers 50 views ### Solving a system of equations and inequalities over the reals I have to solve the following system:$$\begin{cases} 16x^4-40ax^3+(15a^2+24b)x^2- 18abx+3b^2 = 0 \\ 5ax-4x^2-b>0 \\ 15ax-20x^2-3b<0 \\ 4x^3-8 c x^2+5acx-cb <0\end{cases},$$where c<0, ... 0answers 68 views ### How do I invert a function with two arguments? [closed] I begin with a function defined by c[u_, mH_] I won't go into details because it comes from countless lines of partial differential equations, boundary ... 2answers 60 views ### Solve equation with Log[s] When i try to solve the following equation, i get error message that "Solve::dinv: ...."due to the presence of Log[s0] term. How to solve this? the code is given below: ... 0answers 42 views ### FindRoot::nlnum & Interpolatingfunction I want to solve a system of differential equations and find a point where the solutions cross. So four steps: 1. Solve the system of differential equations: ... 1answer 87 views ### System of differential algebraic equations with one of the variables as an argument of the other varaibles This is my first question here and I don't even know what to search for to find a solution. So I'd appreciate it even if someone can point me in the right direction. EDIT: My post had many problems, ... 1answer 42 views ### How to find function existence border I have a function like this f[x_, a_] = Log[-x - a]*(-x - a) + Sin[a]; this function does exist if x > a because of Log[]. a - parameters. if I plot a few graphs ... 1answer 77 views ### How many solutions do you get from simultaneous polynomial equations? I have the following four simultaneous polynomial equations ... 1answer 107 views ### Is the output to Solve ordered or are the solutions randomly placed? I am trying to find the roots of a polynomial of eight degree$$\sin^8\varphi-2\lambda_i^2\sin^6\varphi+(6\lambda_i^2+\lambda_i^4)\sin^4\varphi-(4\lambda_i^2+2\lambda_i^4)\sin^2\varphi+\lambda_i^4=0$$... 1answer 84 views ### How to estimate the running time of a programme on mathematica [closed] I am solving a system of 6 linear equations containing six unknowns using mathematica. It is taking too much time and still running after 3 hours. can I estimate the approximate running time? Is there ... 1answer 96 views ### Putting as many expressions as possible equal to zero Say I have a list of expressions involving many different variables. I would like to see how many of the expressions I can set equal to zero thereby solving for some of the variables in terms of the ... 2answers 186 views ### the exact real solutions of cubic polynomial? Such as the equation:x^3-5 x+1=0, according to the cubic discriminant we know it has three real solutions. We can also find the exact expressions of them from Mathematical handbook. However, by MMA ... 0answers 51 views ### Can Mathematica give the solutions to x^n - 1 = 0 in their radical form [duplicate] If I input: Solve[x^3 - 1 == 0] Mathematica returns: {{x -> 1}, {x -> -(-1)^(1/3)}, {x -> (-1)^(2/3)}} I want to see the roots expressed as radicals for ... 2answers 215 views ### General solution for a linear ODE set with complicated coefficient This is the original problem that motivated me to ask this question. I encountered it when trying to reproduce the deduction in this paper. (I'll paste the relevant part below to make this question ... 1answer 253 views ### Complicated symbolic coefficient slows down equation solving Here's a simple example for Solve: ... 1answer 104 views ### How to approximate the solution of a system of quartic equations In an attempt to evaluate the point at which the cycle 2 becomes unstable for the given map: $$x_{n+1}=μ-x_n^4=f(x_n), \quad μ \in \mathbb{R}$$ I have so far managed to ... 2answers 82 views ### Solving system of equations in Mathematica I am unable to solve this system of equations in Mathematica. Where the third equation takes value (on the right hand side) from 0.00001 to ... 1answer 179 views ### How to tell Solve[] to satisfy as many constraints as it can? Is there any way to tell Solve (or something similar) to return values for variables that solved as many constraints as it happened to satisfy? Edit: I had ... 1answer 66 views ### How to get rid of the derivatives in the solution? [closed] I have this system equations: ... 1answer 70 views ### Is it possible to stop NSolve when it finds a single root [closed] I have a system of nonlinear algebraic equations with following property: if (x_1,x_2,x_3,x_4,x_5,x_6,x_7) is a root of the system, so any its permutation is another root as well. My system contains ... 6answers 260 views ### Roots of a characteristic equation. Can Mathematica solve it? I have been using Mathematica for a few years, but with basic things. Now I need to find the first 10 roots of the following equation: ... 3answers 456 views ### Writing Mathematica's Root function output in a academic paper form I need to write the following (which is the result of a Solve command I ran in Mathematica) in an academic journal paper: ... 1answer 80 views ### Transforming from implicit Cartesian form to a parametric form [closed] First equation ((1.2 x)^2 + (1.4 y)^2 - 1)^3 - (1.3 x)^2 y^3 == 0 I wanna transform it into a parametric equation. I spent a much of a day working on it without success. The equation describes the ... 1answer 94 views ### Trying to find a temperature profile with a nonlinear 2nd order ODE. NDSolve very sensitive to seemingly arbitrary constant I am trying to solve this differential equation for a heat transfer problem: kt\frac{\partial^2 T}{\partial x^2} = \epsilon \sigma T^4, \ \ \ T(0) = T_0, \ \ \ \frac{\partial T}{\... 3answers 85 views ### Interactive Application using Manipulate for Fibonacci Series I am working on creating interactive app using Manipulate function on fibonacci series using SeriesCoefficient. I want to plot the fibonacci numbers based on the slider of Manipulate function. I have:... 1answer 66 views ### Reduce is not giving answers, only verifies it's true I'm trying to find a range for {q1,q2} with the conditions listed such that U1R >= U1S ... 1answer 148 views ### loops and data file I have solved a set of equations for a specific given data point and restricted my solutions to 100. then I did TrimmedMean to have the mean value of all 100 ... 0answers 32 views ### Solving for limit of integration with a piecewise function (FindRoot vs NSolve) [duplicate] I am trying to solve for the limits of integration using a piecewise function. I'm doing this in a loop over a list of data, mostly because I'm not well-versed enough in Mathematica to make this a ... 2answers 192 views ### Solve System of Equations with Constant Ratios I'm currently trying to use Mathematica to solve a problem for my fluid mechanics class. I need to solve the following system of 3 equations:$$\begin{align*} \dfrac{h}{a} &= \cot \left(\dfrac{h/...
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I have a quick question: in question:Solving an ODE with boundary conditions at infinity and 0//different problems, I asked for help concerning a differential equation- however, the whole solving ...
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### find indeterminates (which are function of time) of an expression [duplicate]

Is there a function in Mathematica so as to find the indeterminates of an expression? When I used Maple, there was the function indets. Is there a similar function in Mathematica? Here an example ...