# Tagged Questions

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

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### Help numerically solve this non-linear PDE with singularity

I have trouble finding a numerical solution to the partial differential equation below. It seems to be a singularity in the solution somewhere, so I searched online and found that it is suggested to ...
69 views

### Using Solve[ ] inside a Module

I want to use Solve[] inside a Module. If I make the variables solved for local to the module, they are treated differently than ...
156 views

### Given $y$, find the $x$ value of a point on a Bezier curve

I have linear equation of Bezier curve with one control point: f[x_] := (1 – t)^2 x0 + 2 (1 – t) t x1 + t^2 x2; f[y_] := (1 – t)^2 y0 + 2 (1 – t) t y1 + t^2 y2; ...
37 views

### Solve inside of InputField is not dynamic

On the 7th line, I have an InputField that I want to dynamically change as I change the input. It solves an equation that is later used to determine the change in y intercept in the graph. However, ...
49 views

### Using solution of an equation [duplicate]

I want to solve something like f(x)=0 and then have the real solution be set as the value of another variable. I can't figure out how to do it. I tried something like this as an example, but it didn't ...
265 views

### Finding an analytic solution of a cubic equation

I have been trying to solve a cubic equation $$y=zy^3 + z$$ in $y$ – that is, my desired result is a function $y(z)$ satisfying the equation. Now, there are three solutions of this equation and ...
173 views

### Randomly generate points on a van der Waals surface

I'm looking to randomly place an atom $\mathbf{A}$ onto a van der Waals surface formed by atoms $\mathbf{B}$, such that the distance between the randomly-generated atom $\mathbf{A}$ and the nearest ...
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### Is this equation true? [migrated]

As the question states, does this equation hold true? $\sum_{j=0}^n \sum_{E \in {n \choose j}} (-1)^{|E|}(n-|E|)! = \sum_{j=0}^n(-1)^j(n-j)!{n \choose j}$ From what I understand, this holds true at ...
98 views

### how to solve a high-dimension system faster, please

I want to solve a high-dimension system as below. If the size is 50, there are 50^2 equations and find the root cost about 6s in my PC. If the size is 100, about 100s. But if size is 500, the time is ...
2k views

### NDSolve with vectors

I'm stumped. I'm trying to write this using vectors, but the 2nd derivative isn't being expanded like I expected it to be. This is a system of equations for a projectile with quadratic drag and ...
34 views

### NSolve on a function with NIntegrate

I have a function defined with an NIntegrate. The function is of x,y,z, integrated across t: ...
43 views

### Solving a system of integral equations

Is it possible to solve a system of integral equations in Mathematica? More specifically, I would like to obtain numerical solutions for $\mu$ and $\sigma$ from the following system: ...
144 views

### Solution of a System of Equations Using Solve

Part 1 I am trying to solve a simple system of equations as follows Solve[{A x^B == f, A y^B == g}, {A, B}] But I just get the error Solve::nsmet: This ...
32 views

### Solve a simple equation for a unknown indexed by a real number

I have the following equation. ...
62 views

### Find a independent variable value from the numerical solutions of a system of differential equations

I have calculated the solutions for the following system of differential equations using NDSolve ...
45 views

### Find a solution to a set of equations, within a specified range

Given the following list myList = {a + 2 g, -2 c d - 3 b f + 2 a g, d^2 f - c d g, -2 c^2 - a f, c d f - c^2 g} of five expressions in the variables ...
208 views

### Approximate analytic solution to a polynomial equation

The analytic solution of the equation $$1-\frac{2M}{r}+\frac{Q^2}{r^2}-\frac{\Lambda}{3}r^2 = 0$$ obtained by using the code ...
58 views

### Proper way to create plot of equation with parameter solutions

for example I am trying to execute this code: ...
87 views

### How to define amazing Goodstein's sequence?

There is an amazing and counterintuitive theorem: For all $n$, there exists a $k$ such that the $k$-th term of the Goodstein sequence $G_k(n)=0$. In other words, every Goodstein sequence ...
252 views

### Law of Cosines to determine angle change along spiral

The Spiral I'm trying to place circles along the outside of an Archimedean spiral. Shown below: ...
175 views

### More issues Integrate, NIntegrate, FindRoot

I'm trying to solve a system of 3 non-linear equations using FindRoot and Integrate. If I start FindRoot[] close to the right answer, it works well but returns a bunch of error messages first. ...
69 views

### Selecting the maximum value from the results returned by NSolve

I'm trying to select the maximum value from the answers Mathematica 7.0 is getting from a simple basic NSolve algebric equation : ...
93 views

### Henon Map Fixed Points Plot versus Iterations and Plot of the Map

For the Henon Map: $$x_{n+1}=y_n+1-αx_n^2, \quad y_{n+1}=β x_n$$ I would like to discover period doubling bifurcations by varying the parameter $α$ and plotting $x_n,y_n$ versus the iterations $n$ of ...
50 views

### BSplineFunction defies numerical solution

I am trying to find an intersection between a straight line and a BSpline. The lines: ...
109 views

### Complicated implicit plotting [closed]

I'm quite new to Mathematica and have already spent tons of time on problems of this type, browsing through tutorials and topics here. I'm now coming to conclusion that it cannot be done and am about ...
60 views

### Getting FindRoot::nlnum when trying to find root of an Interpolating function [closed]

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: ...
66 views

### Estimating processing time for commands [closed]

I am trying to evaluate some equations by using Taylor series of expansion (Series[], ExpandAll[], and Normal[] command), and using n equation and n unknown (Solve). Following is not full command (if ...
44 views

### Help Compiling Vectors using Iterations

So I have a nice code that runs properly, which I include below but, in my naiveté, I'm having issues iterating my procedure. Simply put, I have a function of two real variables $f(x,y)$ and I want ...
166 views

### Solving my graduation exam geometry problems with Mathematica [closed]

How capable is Mathematica when it comes to typical school geometry problems? Is there a way to throw constraints at it and get it to spit out a solution? Here are two geometry problems from my ...
81 views

### Finding zero of nonlinear simultaneous equations [closed]

I'm trying to find the zero of nonlinear simultaneous equations defined in myfun1 and myfun2: ...
65 views

### Finding Real Roots and Determining Range

I am interested in determining the minimum and maximum values of the real roots of polynomials of form $P(x)=\sum_{k=0}^n a_{k} x^k$ where $n$ will have a defined value (say 3,4,5...) and $a_k$ are ...
80 views

### Finding and plotting a parametric solution to a complicated equation (transcendental, log-polynomial)

I am trying (desperately) to find a way to solve a transcendental equation whose solution $x$ depends on non-numerical parameters $a$ and $b$. And then to produce a ...
192 views

56 views

### Plotting the results from Solve in a Manipulate expression

I am a self-taught Mathematica user, trying to make some progress. This is my code: ...
67 views

### Solving an equation entered by the user via the Input function

I am new to Mathematica. I am trying to create a program that takes in an equation from user input and then gives the answer. I started with a manipulate function as I created a similar program for ...
When an equation has multiple solutions, how do you find the first solution? Example: Say we're trying to find the first positive x-intercept of the cosine function: $cos(x)=0 \land x \ge 0$ ...