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

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0
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2answers
21 views

Solve simple trig equation

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 ...
0
votes
0answers
37 views

Solve a function to find the optimum value of parameter in mathematica

I have a complicated function as shown It doesn't have a standard integration as far as I know. Now, numerical integration of the left hand side function over a set of points gives the right hand ...
2
votes
1answer
232 views

What is wrong with FindRoot?

I am trying to find a numerical solution to the following transcendental equation ...
0
votes
1answer
41 views

Strange Simultaneous Equations [on hold]

Solve the simultaneous equations: 70-T=7a T-40=4a By multiplying both sides of the equations by a factor and shifting the terms I transformed them into the following form: -28a-4T=-280 ...
3
votes
0answers
61 views

NSolve doesn't work on an equation containing a numerical integral and constraints

I'm having trouble getting Mathematica to solve equations numerically. I know that its important to specify the type of variables for pattern testing (see e.g. here) but this doesn't seem to work. ...
0
votes
0answers
70 views

Solve won't solve $x = y^2 - z^2$ for $z$ [on hold]

Although this equation can be solved in my head, it's bugging the crap out of me that Wolfram|Alpha can solve this, yet Mathematica can't. I'm trying to solve this equation for z: $\quad \quad x = ...
2
votes
2answers
142 views

How to solve this two algebraic equation simultaneously for u and H ?(all real number)

I want to find the non-zero value of H when beta is changing(especially what value of beta when increasing will there be a non-zero H value). H is between [0,100]. This is actually the calculation ...
2
votes
1answer
52 views

2D plot using output from the other function

I would like to get 2D plot using output from the other function. FindInstance[0.5*x^2 + Cos[y + P] == 1, {x, y}, Reals] By changing values of P manually it gives ...
0
votes
0answers
35 views

Numerically finding a single root of a polynomial system

I may be off base, but from the documentation, it sounds like NSolve is specifically tailored to finding (all) roots of a polynomial system. On the other hand, ...
4
votes
3answers
132 views

My evaluation is taking a lot of time

I was evaluating the roots of a transcendental equation, when I noticed that Mathematica never finishes but stays in the running state. The following is the code that I was using: ...
0
votes
0answers
30 views

Nested optimization (in a dynamic game) [on hold]

I have a dynamic game in two stages with two players. The solution of this game requires first to find the Nash equilibrium in stage 1 with correct expectations of the decisions taken at stage 2. At ...
4
votes
1answer
74 views

Points on discriminant variety?

I am trying to find a way in Mathematica to compute points on discriminant variety for modest size systems, but I couldn't find one. The system is something like: ...
1
vote
1answer
67 views

solving a non trivial equation system

I try to solve a 4 equations, 4 unknowns system. Here is my code ...
0
votes
1answer
90 views

Reduction of an Inequality in $\mathbb{C}$

Reduce[ Abs[-((4 p)/(-1 + Sqrt[1 + 4 p + 4 q])^2)] + Abs[-((4 q)/(-1 + Sqrt[1 + 4 p + 4 q])^2)] < 1 , Abs[p]] It is taking lot of time. It is running. Can ...
0
votes
0answers
17 views

Require Formula to work out size of Share Units with given variables [closed]

Formula required to find out size of Units at Break even point given various variables. The variables A, B, C are the differences between 3 separate Levels in price and a new common take profit level ...
4
votes
1answer
100 views

Why doesn't NSolve work for this equality? Wildly incorrect solutions are given in certain cases

I am trying to write a function that solves for p in the following equation: PDF[BinomialDistribution[n, p], x] == op The ...
2
votes
1answer
54 views

RootReduce-Part of Solve

I have given the following expression in $M$ and $z$: \begin{equation} a = \frac{-4 M^2+M (-3 z-5)+\frac{1.1875 z}{\sqrt{\frac{0.015625 z}{M+1}-1.5625} \sqrt{\frac{0.765625 ...
3
votes
0answers
53 views

Method of characteristics, recursion formulas

I'm helping a friend out with a problem. He needs to plot out the solution to a water surge in a pipeline. I have all the parameters set and I've put the equations in Mathematica, but I can't get the ...
-2
votes
0answers
42 views
2
votes
1answer
95 views

How to solve coupled complex-valued equations faster and get simplified solution

I have six coupled equations. How to solve these equations symbolically faster in Mathematica. In these equations, variables p,q,x,y are ...
1
vote
2answers
143 views

Trying to solve a system of equation

I am trying to solve 3 equations 3 unknown system on Mathematica in order to get numerical results for my three variables x,y,z but the software is always on the ...
1
vote
2answers
62 views

Condition on Inside of Region

How do I handle boundary conditions present in the region. Mathematica complains about the condition v [1 , t ] == u [1,t]. The condition should be given to this ...
3
votes
1answer
46 views

Reduce return a strange result for solving a equation with radical

Reduce[1/Sqrt[x] == x + 1/(Sqrt[2] + Sqrt[3]), x] the output is unreadable and include the symbol Reduce`CADAlgVar[1].
0
votes
1answer
58 views

what am i missing? [closed]

An attempt to solve ...
4
votes
0answers
54 views

Reduce doesn't solve this equations with condition

Reduce[{4==Abs[-1+2 Cos[2A]+2 Cos[2B]+2 Cos[2(A+B)]]},{A,B},Reals] worked well, but ...
1
vote
0answers
25 views

Minimizing values of expressions dependent on more variables [closed]

I need to enforce seven expressions dependent on seven variables to be zero. However, the expressions are quite complicated and generaly I get a system of transcendental equations which only sometimes ...
17
votes
3answers
485 views

How to find numerically all roots of a function in a given range?

It is common that I search numerically for all zeros (roots) of a function in a given range. I have written two simple minded functions that perform this task, and I know of similar functions on this ...
0
votes
1answer
59 views

NDSolve does not satisfy initial conditions

For the problem I'm facing, I have three coupled diff eqns that I'm trying to solve ...
0
votes
2answers
84 views

How to solve a pair of coupled 2nd order equations using shooting method

I have a pair of equations for x[t] and y[t]. Both are 2nd order and they are coupled. Now say that I know the following ...
0
votes
0answers
54 views

Equations in a quadratic field

I would like to solve a system of equations in a quadratic field, meaning that each variable $x$ of my system can be written $a + b \sqrt{d}$, where $d$ is a fixed value. Suppose for example that I ...
3
votes
1answer
107 views

Computing planet conjunctions with 2D circular orbits still hard?

All methods I've seen for computing planetary/stellar conjuctions (when two planets or a planet and a star appear close together in the sky because their angular separation, as measured from Earth, ...
-1
votes
1answer
79 views

What am I doing wrong when using Solve ( Wolfram Alpha)

It is not because we do not interpreted correctly WolframAlpha["Solve[64(!(*FractionBox[(x - *SqrtBox[(*SuperscriptBox[(x), \ (2)] - 1)]), (x + 1)]) !(*SuperscriptBox[()), \ ...
3
votes
1answer
87 views

How to change parameters to equations of physical properties they belong to in an equation?

First off, I want to apologize for my poor English as I am not a native speaker. In my physics research, I had to solve a system of equations, from which I would get a solution for the speed of an ...
4
votes
4answers
161 views

How to find roots of equation

Solve[(Cos[θ] - Cos[θi]) + (θ - θi)*Sin[θi] == 0, θ] Hi, I am new to Mathematica, and I am trying to find roots of the above equation, but not success.
1
vote
0answers
70 views

Solve struggling with two equations in two unknowns

I have a two equations and two unknowns. I tried to solve the equations with Mathematica, but it is having trouble. It has been saying Running... for quite a long time. Here is my system: ...
0
votes
1answer
57 views

Problems with solving two coupled lorenz equation with NDsolve

I have a system of two coupled lorenz equations and I'm to integrate it: ...
6
votes
1answer
109 views

Why is Solve slow for one representation and fast for an equivalent form?

When I try to solve the following: Solve[(1 - (-1 + x)^- x)^8 == 95/100 && x > 1, Reals] solve chokes. If instead I use the equivalent form: ...
2
votes
1answer
52 views

Most simple example where series expanding a root object actually fails due to branchcuts

When computing the series expansion of a Root object Mathematica throws an error like: "Because of branch cuts, the series may represent a different root of [root expression] for some values of ...
0
votes
0answers
57 views

The system can not be solved

I'm trying to solve this equation: f[a_][r_]=((a*r/12)*(1+(r/12))^n)/(((1+(r/12))^n) - 1) When I type Solve[f[a][r]==p, a] ...
2
votes
1answer
105 views

Solve overdetermined set using Mathematica?

As shown below, this is a overdetermined system. Could you teach me how to find the optimized solution in Mathematica? I know it could be solved by the method of least square, but how to realize it in ...
1
vote
2answers
141 views

Solve a symbolic underdetermined Linear System

Dear StackExchange Community, I'm trying to solve an indeterminate linear system of equations, with $n+1$ variables and $n$ equations; therefore, I need to express all $n$ other variables a function ...
0
votes
0answers
38 views

How to solve algebra equations containing integration and parameters?

I'm trying to solve two nonlinear algebra equations for two unknown parameters, U and Tf. Since some terms in these equations contain integration, and the integration also contains U and Tf. The main ...
3
votes
0answers
71 views

Solving for the roots of a trilinear system of polynomials

I have been trying to solve for the roots of the following system of trilinear polynomials: ...
0
votes
0answers
40 views

solving dynamic system by a finite difference equation approximation

I have a four dimensional dynamical system from optimal control model. I have 2 states and 2 control variables. I have already found the corresponding initial conditions for two control variables for ...
0
votes
2answers
53 views

How to find ANY solution to an underdetermined system of equations?

I have certain systems of equations for which I need ANY solution if one exists. Can I get MMa to just do that? This doesn't work: ...
0
votes
2answers
91 views

Find *all* numerical solutions to cosine based equality

To help with http://astronomy.stackexchange.com/questions/11456/ I'm trying to find all numerical solutions to: 5.20427*Sin[0.529699*t] == Sin[2*Pi*t] Since the period of the first function is ...
2
votes
1answer
126 views

Solving SDE: $\frac{dy(t)}{dt}=(c+\sigma_wW(t))y(t)+\epsilon(t) $ in Mathematica

I want to solve this differential equation $\frac{dy(t)}{dt}=(c+\sigma_w W(t))y(t)+\epsilon(t) $. For details see ...
2
votes
0answers
40 views

NDSolve with NIntegrate [duplicate]

I'm new to Mathematica and I'm trying to use it to solve some equation like: NDSolve[x'[t]+NIntegrate[x[tau],{tau,0,t}]==20,x,{t,0,10}] But it keeps giving me ...
1
vote
1answer
47 views

Matrix issue with NDSolve

I am solving a differential matrix equation with NDSolve. ...
2
votes
1answer
92 views

Problem in understanding PDE solution

I solved the PDE shown below and I got the solution. I am new to this tool. In the solution, I have a constant multiplied by a vector like function (please refer second term of the solution). What ...