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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Multiple layered FindMinimum

I have a function SQ[b, zQ, zh] where I can find at which zQ it is a minimum, b=0.1 and <...
104 views

Integration NSolve problems

I have some problems in solving this equation numerically in Mathematica. Mathematica gives me the error message "NSolve::nsmet: This system cannot be solved with the methods available to NSolve&...
31 views

How can I set the plot range to the point where the function becomes zero?

I have a lot of functions (mostly exponential included and more precisely complicated combinations of Gaussian and Slater ones) which decay and become zero in the different points depending on the ...
126 views

Calculate median of pdf using NSolve [closed]

I was trying to compute the median of a pdf using NSolve, defined such that $$\int_{0}^{\rm median}p(x)dx = \frac{1}{2}$$ but NSolve seems unhappy about solving for an upper limit of an integral. A ...
40 views

How to get the average x of a density function?

I have this code: ...
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How to format linear equation solve

I need to solve the system of linear equations $S_i = \sum_ {r = 1}^\lambda x_ {r, i} E_r$, where $S_i$ is a $\lambda$ - dimensional vector, $i$ runs from 1 to $n$, $r$ runs from 1 to $\lambda$,...
58 views

Solve cannot return NOT[A==B] in equations results

can you help me to return NOT[A==B] for Solve operation. in below code it does not return zP!=14 ...
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How to remove the domain of variables in result relation?

this is my relation and it returns me xP [Element] Integers. I do not want any kind of these information. for example, I just need to see for every relation, yp-> x+1 - xp , thanks ...
155 views

How to plot this implicit function? [closed]

The command ContourPlot[{RealAbs[x + 1/y] + RealAbs[10/3 - x + y] == 10/3 + y + 1/y}, {x, -5, 5}, {y, -5, 5}, PlotPoints -> 50] , as one sees, draws ...
43 views

Get Real Solutions works in Solve but PositiveReals don't (Quantities)

I'm trying to get the R+ Solutions to a school problem with solve. Everything works fine with Dom -> Reals but when I try ...
75 views

Solve a differential system of equations in time

I am trying to solve a system of 3 equations and 3 unknown variables that change in time (Tw(t), Tcor(t), Texit(t)). ...
88 views

Why does Solve produce a result in terms of one variable, but not the other?

I have the following quartic equation:\begin{equation} x^4 + ax^3 + bx^2 + ax + 1 = 0 \end{equation} and I'm trying to find relations for $a$ and $b$ for which we have multiple roots. To this end, I ...
60 views

How to get a single solution by simultaneously solving three equations with three variables? [closed]

I'm trying to solve the following three equations having three variables. ...
51 views

NDSolver cannot give precise result for extremely small values

I would like to solve an ODE with MMA. The equation is simply the Coulomb law. However, I cannot get a satisfying result: ...
79 views

How can transform the question into Wolfram language? [closed]

I've been sitting with this question: A graph has 7 corners. The degree of each corner of the graph is 3 or 4. How many edges does the graph contain if both degrees are represented? And this is the ...
48 views

Defining new Domain for variables

I am trying to define a new Domain for variables to use with functions like FindInstance or Solve. For example, If I wanted to solve x+y+z=1 over the Reals, I'd get a large solution space. But If I ...
65 views

Trying to solve a basic Lagrangian optimisation problem

New to Mathematica, trying to solve a simple economics problem but having troubles with using Solve and Eliminate. The question: Now suppose that this agent makes two choices, expressed by x and y ...
111 views

How to solve \[Theta]23 from the following equation?

How do I solve [Theta]23 from the following equation? ...
141 views

Solving implicitly a trigonometric equation

I am trying to solve this equation with respect to L: L== ((9.81*T^2)/(2*Pi)) Tan[2Pi*d/L] Since you have the unknown ...
84 views

Assigning A Symbol To A Second DSolve Solution

I am looking for a way to compress a lengthy DSolve solution to a single symbol, kind of like assigning a variable. I have this expression: ...
71 views

how to get the result without conditional expressions

I am working with JAVA API and send a relation to kernel, then receive the returned solved result. Although I explicitly mentioned in my relation to have Integer Elements, the returned expressions ...
37 views

How to solve two IntegerPart function in Reduce?

Here I have two Functions, which involve IntegerPart. For example: f[x_] := IntegerPart[-0.002*x*(x - 1000)] q[x_] := IntegerPart[-0.002*x*(x - 2000)] Then I want ...
111 views

Find relationship between parameters to prove conditions of eigenvalues

I have the following 3-by-3 matrix. I need to find condition(s) on the parameters 'a' and 'b' such that this matrix has exactly 1 eigenvalue bigger than 1 in absolute value and other two eigenvalues ...
147 views

Obtaining inequality between two variables

I have two variables ...
70 views

Can mathematica numerically solve this system of coupled integro differential equations?

Here's my system: R(x,y,t) is the concentration of a chemical that's diffusing across the box. The disk is a mobile sink for the chemical, which absorbs it in proportion to its concentration. The ...
39 views

Introducing FindRoot in a ReccurrenceTable but problem with the starting point

I would like to introducing FindRoot in a RecurrenceTable, that uses the previous result as a starting point. My equations are defined as following: ...
81 views

How to find a matrix satisfying following equation

I have a $N \times 1$ vector $F(t)$ for $0\leq t \leq 1$. I want to find a $N\times N$ Matrix $C$ (a real-valued matrix) satisfying the following equation: $$\int_0^t F(t_0)dt_0= C.F(t)$$ If it ...
161 views

How do I improve this code for hyperbolic numbers so to allow equation-solving?

I have the following code, which allows evaluating expressions with split-complex unity J: ...
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Rewrite a variable in terms of another variable

I have two variables t = 1/Sqrt (Sqrt[1 + Cos[a]] + Sqrt[1 - Cos[a]] + Sqrt[1 + Cos[b]] + Sqrt[1 - Cos[b]] + Sqrt[1 + Cos[c]] + Sqrt[1 - Cos[c]]) and <...
I want to solve this system of two equations for $x$ $$\{ \sin (2\pi x)+\sin (\frac{2\pi}y)=0 \quad , \quad \cos (2\pi x)-\cos (\frac{2\pi}y)=0 \} \qquad (1)$$ I use ...