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

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33 views

Solving a system of non-linear equations / approximate or exact solution — either takes ages or gives non-sense

I would like to find all solutions in terms of functions F and g of the following equation $h(x)=\int_0^x F(x-y)g(y) dy$ Normally $h(.)$, $F(.)$ and $g(.)$ are continuous. But I have a numerical ...
0
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0answers
23 views

Solving a consistent overdetermined linear system

Not a duplicate question. I already tried all the Answers offered for this Question and they failed, so I believe this is a different problem with Solve[]. I have a solveable, consistent system of ...
0
votes
2answers
86 views

After NumberForm I cannot apply a Sine function. Why? [duplicate]

After NumberForm I cannot apply a Sine function. Why? This works: sol1 = x /. Solve[x^2 - 3 == 0, x] Sin[sol1] Output = $\{-Sin[\sqrt{3}],Sin[\sqrt{3}]\}$ Also ...
-1
votes
1answer
49 views

When NSolve for X, Y, only output solution for X

I have an NSolve with two equations and two unknowns (X,Y). There is a unique solution. NSolve currently gives me the solution pair (X,Y). But I only want to read out one of the variables (say X). ...
0
votes
1answer
83 views

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

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
2answers
632 views

Solving simultaneous exponential equations

In[1]: Solve[{(1 + k)^n == 0.6, (1 + k)^(n + 1) == 0.3}, {n, k}] Solve::ifun: Inverse functions are being used by Solve, so some solutions may not be found; ...
1
vote
3answers
155 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 ...
2
votes
1answer
242 views

What is wrong with FindRoot?

I am trying to find a numerical solution to the following transcendental equation ...
0
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1answer
46 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
65 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. ...
2
votes
2answers
144 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 ...
0
votes
0answers
75 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 = ...
4
votes
3answers
134 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: ...
13
votes
3answers
4k views

Find all roots of an interpolating function (solution to a differential equation)

I'm trying to find all the roots of the solution to a differential equation. Using NSolve or Reduce I don't get the roots, so I'm using an iterative method which I found in physicsforums.com. This ...
4
votes
1answer
76 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: ...
2
votes
1answer
55 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 ...
7
votes
0answers
115 views

How does Mathematica resolve symbolic systems of inequalities?

Before getting into my question, let me provide some context: I recently started using Mathematica to automatically perform stability analyses that I previously did by hand. A major part of the ...
0
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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, ...
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
30 views

Nested optimization (in a dynamic game) [closed]

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 ...
1
vote
1answer
68 views

solving a non trivial equation system

I try to solve a 4 equations, 4 unknowns system. Here is my code ...
1
vote
1answer
129 views

Optimization for inequalities in $\mathbb{C}$

I want to check when the expression $$ \sqrt{\sqrt{\lambda^{2}\left(2E+\lambda^{2}\right)}+E+\lambda^{2}} $$ is real, when it is purely imaginary and when it is complex (with imaginary part not ...
0
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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 ...
1
vote
1answer
112 views

In which condition releated to thee coefficients some equation has a solution

Please excuse me if the question seems to commonplace. Can Mathematica give a response to this question: In which condition related to the coefficients $c>0, \, n\geq 2, 0<p<1,\, a>c$ ...
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 ...
1
vote
1answer
71 views

Reduce with for all and implies

I have the following question. p1 = a (1 - c + a) p2 = b (1 - c - b)/((1 - b)^2) v1 = (x^1.5 - 3*x)*p1 v2 = x*p2 I want to find x ranges which makes v1>v2 under ...
4
votes
1answer
127 views

Finding and plotting roots with parameter

I have the following function: $$u(x,t)=\sum_{k=1}^\infty\frac{v_0 L}{\lambda_k c \sin\left(\lambda_k\right)}\sin\left(\frac{\lambda_kx}{L}\right)\sin\left(\frac{\lambda_kct}{L}\right)$$ and this ...
1
vote
0answers
73 views

Help inteprete the solution given by reduce

I am trying to solve for a2 in the equation below: ...
0
votes
3answers
91 views

Diophantine and odd

need to resolve this Diophantine equation, but with the condition that a, b, c belong to the set of odd numbers from 1-51, as I write this condition in the code ...
11
votes
1answer
1k views

What are the algorithm details of FindRoot?

The Help page of FindRoot says: "by default, FindRoot uses Newton's method (Newton-Raphson) to solve a nonlinear system". But I ...
8
votes
1answer
187 views

What are the hidden specifications for FindRoot

The Help page of FindRoot says: "by default, FindRoot uses Newton's method (Newton-Raphson) to solve a nonlinear system" (or a nonlinear equation I ...
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 ...
3
votes
0answers
54 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 ...
10
votes
5answers
2k views

How to get exact roots of this polynomial?

The equation $$ 64x^7 -112x^5 -8x^4 +56x^3 +8x^2 -7x - 1 = 0 $$ has seven solutions $x = 1$, $x = -\dfrac{1}{2}$ and $x = \cos \dfrac{2n\pi}{11}$, where $n$ runs from $1$ to $5$. With ...
1
vote
1answer
85 views

Fitting with roots of transcendental equation

I'm new to this community and my first question probably reflect my lack of confidence with Mathematica. My problem is the following: I find the roots of a transcendental equation dependent on a ...
0
votes
1answer
113 views

NSolve cannot find the solution

I have some data which looks like: ...
2
votes
3answers
127 views

Solving equation containing Erf expressions

Given the equation below, how do I find the value of b so that the function is equal to 21. I tried solve but I keep getting an error message. ...
17
votes
3answers
487 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 ...
22
votes
8answers
5k views

About multi-root search in Mathematica for transcendental equations

I have some questions for multiroot search for transcendental equations. Is there any clever solution to find all the roots for a transcendental equation in a specific range? Perhaps ...
3
votes
1answer
126 views

Solving a system of generated equations?

I would like to generate a function in the following form, where the number of terms can be specified arbitrarily: ...
1
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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
5answers
192 views

Finding roots of transcendental equation and collecting into a list

I am working on a physics reserach project for school and I have run into some troubles working Mathematica. I am a fairly inexperienced mathematica user so any help would very much be appreciated. I ...
2
votes
1answer
246 views

why doesn't NSolve find all the solutions that Solve finds?

Define d[p1_, p2_] := (p1 - p2).(p1 - p2) to be the square of the distance between two points. I am trying to solve equations like: ...
4
votes
1answer
2k views

NSolve: Mathematica 9 issue

Bug introduced in 9.0 and fixed in 10.0.0 In Mathematica 8 the following expression evaluates and returns a result in terms of InverseFunction: ...
2
votes
1answer
128 views

Computing Poincaré symbolic solution for an arbitrary integer order polynomial

In the 1880s, Poincaré created functions which give the solution to the nth order polynomial equation in finite form. These functions turned out to be "natural" generalizations of the elliptic ...
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 ...
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 ...