# Tagged Questions

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

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### Assign the results from a Solve to variable [closed]

I am a new user. I know, that my question was already asked billion times before, for example here, but I still cannot adopt these answers to my problem. In my problem I am solving the equation and a ...
58 views

### Newbie Issues with Solving & Plotting a System of equations

I'm having some problems with my mathematica code, I think I'm overlooking something simple. I get valid solutions for u0 thru u4, but it doesnt generate any plot at all. Also, I'd really like to plot ...
119 views

### Solving in Mathematica

I am trying to solve system of equations and inequalities in Mathematica. I am having the doubt that how much of preliminary processing should I do before solving. For example, consider a system of ...
61 views

### NIntegrate over statistical variables with parameter

Essentially, what I am trying to do is the following: Integrate a function which contains the parameter k ...
167 views

### Does LinearSolve know that I gave it a Sparse lower triangular matrix?

Let $\mathbf L$ be a nonsingular numeric (non-symbolic) large, lower triangular sparse matrix. Let $\mathbf b$ be an appropriately sized vector. I want to solve $\mathbf L\mathbf x=\mathbf b$. ...
75 views

### Solving a system of vector equations

I had a problem where I had to solve a series of equations where some of the variables can take multiple value such as shown below ...
90 views

### Find Values of a and b for a Limit

I am having trouble finding the values of a and b for which $\lim \limits_{x \to 0}$ $(\frac{\sin (ax) + bx)} {(x^3)}) = -32/3$. In Mathematica I have entered: ...
86 views

### Evaluation to true using DSolve - syntax errors?

Probably a stupid question, apologies, but I am getting an annoying error when I try to evaluate the following simple PDE $\frac{\partial C}{\partial t} = d \frac{\partial^2C}{\partial x^2}$ between ...
127 views

### Numerical solve question

Why does this work? Solve[5 Tan[t] + 9 == 0 && 0 <= t < 2 Pi , t] {{t -> π - ArcTan[9/5]}, {t -> 2 π - ArcTan[9/5]}} But this doesn't. ...
76 views

### Solve a simple vector equation

I have a vector x = {1, 2, 3} and I want to solve for y such that 5 + x == y which ...
157 views

### How do I solve for a variable inside a sum but independent of the summation index?

How would I go about solving the following for c? Solve[0 == Sum[(t[i]*m[i] - c*t[i]^2)/s[i]^2, {i, 1, n}], c, Reals] I get ...
73 views

### Reducing solutions of Sin[2t] Sin[t] == Cos[t] to a simpler form [closed]

I evaluated Solve[Sin[2 t] Sin[t] == Cos[t] && 0 <= t < 2 Pi, t] And got these results. ...
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### Extending Bresenham's algorithm for subpixel rendering

Original Bresenham's line drawing algorithm it limited to drawing lines between two integer pixel positions and does not allow subpixel rendering. However with my reformulation of this algorithm as a ...
94 views

### Solve equation with sum in it

Have trouble to solve this equation. Anybody knows where're the problems? ...
154 views

### Bifurcation diagram for 1D ising model

I'm new in Mathematica, I want to plot a bifurcation diagram for a complicated Ising system with dynamics that I'm working on, but to get familiar with how to perform it on Mathematica I wish to start ...
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### How to solve trigonometric equations

I have the following problem: I need to solve the equation: $$\frac{\cos\left(x\right)}{x^6} - \frac{6 \sin\left(x\right)}{x^7}==0$$ and I don't really remember how to do it symbolically. Some help ...
120 views

### Solving a functional equation

Suppose I have two functions f[x,y,z] and g[x,y,z], both analytically defined. I want to solve for a function ...
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### Solve 4 equations using Solve [closed]

I'm trying to solve $4$ systems of equations with $4$ unknowns. There are some trig involved and I keep getting error "Solve::ifun: inverse functions are being used by Solve." Please help me to ...
103 views

### Inverse of parametrized ellipse area

If you parametrize an ellipse (with the center, not a focus, at the origin) as: {a Cos[t], b Sin[t]} the area traced out from the focus (not origin) for a given ...
73 views

### How to use the variables from Table in calculation

New to the site and Mathematica. I'm trying to use the finite element method to get a temperature profile. So if $q_0=f(T_0,T_1)$, $q_n=f(T_{n-1},T_n)$ and we also know that ...
83 views

### How to solve nonlinear equations involving integrals

Sorry, if this is a duplicate, I was not able to find a corresponding answer. The only question related to mine, as far as I can see it, is this one: How to solve algebra equations containing ...
108 views

### Solving coupled ODEs with NDSolve to fit experimental data

I need to fit a multi-exponential data (Intensity x Time) using a model consisting of three differential equations. I want to find the parameters that gives the best fit to the experimental data. ...
198 views

### Not getting expected result from numerical evaluation of solution given by Solve

Let $m$ be a large integer and $z\in (0,1)$. I want to find $0 < k < m$ such that $\frac{\sqrt{5-\frac{4k}{m}}-1}{2} + \frac{m-\frac{k}{2}\sqrt{5-\frac{4k}{m}}}{m^2\sqrt{5-\frac{4k}{m}}}$ is ...
263 views

### How would I write iterative code to try multiple coefficients for an equation?

So, I'm trying to solve a class of equations, and get all the solutions in a list. The general form looks like this: c == a*Sqrt[1-n] PlusMinus[b * Sqrt[n]] ...
283 views

### Fast calculation of discrete logarithms

Does Mathematica have any built-in fast algorithms for calculating discrete logarithms over $(\mathbb{Z}_p)^\times$ (the group of integers modulo $p$)? Essentially, for a fixed large prime ...
77 views

### Find where a function does not depend on one of its argument

Say I have a function $f(x,y)$ with $x$ and $y$ in some domains. How do I find the subdomain in $y$ for which $f$ does not depend on $x$. My special case one could consider as an example: I have ...
103 views

### Problem in solving a simple Laplace equation

I am trying to solve the following Laplace PDE in MMA: $$\frac{\partial^2 T}{\partial x^2}+\frac{\partial^2 T}{\partial z^2}=0$$ subject to the boundary conditions: \frac{\partial T}{\partial ...
323 views

### How can I use Mathematica to solve a Stefan Problem using an explicit scheme?

I would like to plot the temperature distribution for a particular case. the problem is stated in the paper, behind a paywall here, summarized as Consider a one-dimensional container of length l, ...
33 views

### Solving and replacing solution for solving again

Given some equation to solve S1=Solve[f[x,z]==g[x,z],x]//Simplify which produces something like x->xsol[z] I write ...
129 views

### Finding equilibria to a system of 3 ODEs with 11 unknown parameters. Looking for the intersection of 3 surfaces

I have the following system of 3 ODEs of 3 variables $(\ell,M,h)$ and 11 parameters $(\sigma_{\ell},\mu_{\ell},d_{\ell},\sigma_M,\alpha_1,\beta,\alpha_2,\nu_M,\sigma_h,\nu_h,d_h)$: ...
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### Using BSpline as initial condition in NDSolve [closed]

I have not been successful in extending a 3D noise initial condition to a 2D situation. I would like to use a "noisy" initial condition to solve a non-linear PDE as shown. I used the following ...