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

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1answer
33 views

How can I get all the possible solutions using NSolve [closed]

How can I get all the possible solutions using NSolve. The following equation has eight analytic solutions. These analytic solutions are obtain using "Solve" as ...
0
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0answers
16 views
1
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0answers
42 views

List within a Do loop , i cant get any values [duplicate]

I am having the following problem. I am trying to get some values from solving an equation and apply them into a list but in the output I get nothing but the symbol of the variable... The code is as ...
6
votes
2answers
158 views

NDSolve and matrix formulation do not produce the same result. Why and which is more precise?

Let's assume a vector of variables $\vec a=(a_1(t),a_2(t),a_3(t))$ and let's assume a following DE$$C\ddot{\vec a}=B\dot{\vec a}+A\vec{a}+\vec F.$$ If $A$ and $C$ are both reversible, than the DE can ...
0
votes
1answer
84 views

problem in solving equation

this happened to me when I try to get (f) which should equal sqrt(3)/2 is there any problem in my formula or what? ...
1
vote
0answers
94 views

Need help solving a polynomial system [closed]

I need help solving the following system of equations: ...
0
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0answers
39 views

NSolve with a term that is an interpolating function

I need to solve this system of equations Log[np[x]] + psi[x] + f[np[x], nm[x]] == 0 Log[nm[x]] - psi[x] + f[np[x], nm[x]] == 0 For ...
2
votes
0answers
50 views

Unusual error message from Solve when called by DSolve

Question 111150 presents an equation nonlinear in its leading derivative ...
1
vote
1answer
41 views

How to solve from a list

I have this equation: $y(t)=aE^{-bE^{-ct}}$ and I have this list: ...
1
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1answer
47 views

Maclaurin Series - Table

I'm starting to learn Mathematica. I have to solved this eq and draw the graph. It is developing a series of Taylor in about x0 == 0. This is my equation to solve ...
0
votes
1answer
82 views

Maclaurin series [closed]

Can someone tells me, why is that not working? I'm starting to learn Mathematica. I have to solved this eq and draw the graph. It is developing a series of Taylor in about x0 = 0. ...
1
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0answers
60 views

Obtaining values from interpolating functions

A similar question has been asked in the post HERE but the current question is more complicated: I have the following differential system ...
-1
votes
2answers
96 views

linear system equation ( trying to solve ) [closed]

I am trying to solve this system 3.7 x1+51.5 x10+71.3 x11-84. x2-16. x3-57.7 x4+89.7 x5-54.9 x6-85.8 x7+57.8 x8-51.3 x9==-36.8 -86.3 x1+5.7 x10-0.2 x11-39.9 x2+52.6 x3-45.6 x4+78. x5+90.7 x6-86.2 ...
0
votes
1answer
52 views

Reduce in NDSolve [duplicate]

Second order ode; neither the trig RHS simplifies nor is the solution obtained readily: ...
1
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0answers
58 views

How to use interpolating functions in NSolve with a piecewise function?

I have a system of two non-linear differential equations that are piecewise, the solutions of which I would like to use to obtain the values of a third variable that is also piecewise. I have trouble ...
1
vote
0answers
86 views

Interpreting Root Objects [closed]

I have solved this system of equations in Mathematica for $x$ where the coefficients of the equations were functions of $a,b$ and $c$. Mathematica then displays real solutions $x$ with constraints on ...
1
vote
1answer
34 views

One system consisting of multiple linear equations [closed]

Hello everyone i apologize if this has been answered before i honestly couldnt find it. The problem im having is that im trying to Define one system with multiple equations something like this: ...
5
votes
4answers
101 views

Using roots to get original equation

I have a list of four rules, that I would like to use to find the original polynomial that produced them. The rules are of the form ...
3
votes
3answers
249 views

Why does FindInstance fail when Solve succeeds on these simple constraints?

Why does FindInstance[{a, b} > 0.27 && a == 10^8 && b == 2, {a, b}] fail even though ...
2
votes
2answers
93 views

How to find the integrand singularity points when having NIntegrate::slwcon:

In order to calculate the closed area of the curve below defined by parametric equation curve02, ...
0
votes
1answer
49 views

Extract solutions of linear system to variables

I need to output the answers from solve into the variables named just as they were named in the solve equations. I have checked out this thread Assign the results from a Solve to variable(s) but ...
7
votes
4answers
474 views

How to find a tangent line with 2 points of tangency for a curve?

Say I have a function like this: f[x_] := 4 x^4 - 9 x^3 - x^2 + 10; Plot[f[x], {x, -1, 2}] It's obvious that there's a tangent line with 2 points of tangency ...
1
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0answers
56 views

Artifacts in the solutions of NSolve [closed]

I have (what I think are) some problems with the precision of NSolve. I'm trying to solve this cubic equation: $a f^3(x)-b f^2(x)-c f(x)-z=0$ for the function $f(x)$ and then plot the following ...
0
votes
0answers
29 views

Finding parameters that give constrained eigenvalues of matrix

I want to obtain the eigenvalues $x_1,x_2,x_3$ of a hermitian, off-diagonal matrix, {{0, Conjugate[d], Conjugate[g]}, {d, 0, Conjugate[h]}, {g, h, 0}}, under the ...
2
votes
0answers
31 views

Solving for coefficients of a polynomial? [closed]

I'm sure I'm doing something wrong here, but I'm damned if I can figure out what. I'm trying to find a cubic function that passes through (0, 270), (1, 312), (2,230), (3,0), but the first way I tried ...
0
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0answers
49 views

Output of NDSolve is useless when the system gets bigger

I have a bridge, which I want to discretize on $n$ stiff rods. To find a solution I wrote the following code in mathematica: ...
0
votes
1answer
78 views

How to solve a system of integral equations [closed]

I am trying to solve a system of equations as follows... f1[t]/3 == (1/3)[Integrate[f3[t], t]] f1[t]/(6/5) == Integrate[f2[t], t] f3[t] == Integrate[f1[t], t] I ...
0
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1answer
52 views

Solving a System of Equations syntax confusion

I have a system of two equations which I would like to solve in terms of a third unknown variable $s$. ...
0
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0answers
37 views

Find Roots of expression with modified Bessel functions [duplicate]

I would like to solve an equation of this type $$A-B\,K_0(\kappa\,r)-C\,K_1(\kappa\,r)=0\ \ \quad \text{with}\ A,\,B,\,C,\,\kappa\in\mathbb{R},\ \text{known}$$ for $r$. I am not aware whether this ...
1
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0answers
33 views

Rearrange generic expression into a quartic polynomial

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 + ...
5
votes
1answer
86 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 ...
0
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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: ...
0
votes
1answer
35 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 ...
1
vote
0answers
48 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 $c<0$, ...
2
votes
0answers
67 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 ...
1
vote
2answers
59 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: ...
1
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0answers
36 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: ...
2
votes
1answer
84 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, ...
1
vote
1answer
41 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 ...
4
votes
1answer
77 views

How many solutions do you get from simultaneous polynomial equations?

I have the following four simultaneous polynomial equations ...
1
vote
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 $$\sin^8\varphi-2\lambda_i^2\sin^6\varphi+(6\lambda_i^2+\lambda_i^4)\sin^4\varphi-(4\lambda_i^2+2\lambda_i^4)\sin^2\varphi+\lambda_i^4=0$$ ...
2
votes
1answer
78 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 ...
2
votes
1answer
90 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 ...
3
votes
2answers
184 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 ...
0
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0answers
50 views

Problems solving differential equation with ParametricNDsolve for certain parameters

I'm working on a simulation of a physical problem for a few weeks now and I'm starting to get really frustrated about it. The problem itself is the stationary case of the heat diffusion equation in ...
1
vote
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 ...
4
votes
2answers
205 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 ...
6
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1answer
250 views
2
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1answer
101 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: \begin{equation} x_{n+1}=μ-x_n^4=f(x_n), \quad μ \in \mathbb{R} \end{equation} I have so far managed to ...