# Tagged Questions

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

208 views

### How to solve three equations with four unknowns iteratively?

I have three equations of the form $\quad \eta = f(N1L, N2L)$ $\quad N1L = g(\eta, R)$ $\quad N2L = h(\eta, R)$ I want to eliminate $\eta$, so that I can get $N1L$ and $N2L$ for a range of $R$. I ...
164 views

### Solving determinant of a Kronecker product of matrices gives a numerical error - why?

I am doing the following steps (code at the end of the post): I start with a 2x2 matrix (smatrix), which is a function of a single variable (u2). I want to set the determinant of this matrix ...
97 views

### Using one complicated equation to reduce another

(Relative noob here so don't assume much!) I need to use a vector equation (with $N-1$ entries) in the general form $y_j(x_{i,j},x_{i,j+1},x_{i,j-1})=0, i=1...3, j=1...N-1; x_{i,0}=x_{i,N}=0$, ...
78 views

### Making a list of terms ordered by product order

I have some expressions f,g,h that are elements of a symmetric tensor algebra. The expressions are generated by a basis ...
328 views

### Is there a relatively quick way to solve my integer-valued equation?

This is a very simple problem. It can be solved by nested Forloops that exhaustively test every possible case, throwing out all non-solutions. Find all the ...
621 views

### How to find the integer solution number of a linear system with inequalities?

I have the following system with mixed equality and inequalities defined as: ...
153 views

### Error when using EquationTrekker

I just got to know EquationTrakker because I need to do phase graphs for my classes. When I load it ...
90 views

### What methods does Solve use?

Could you tell me which method that Solve applies to solve linear and polynomials equations?
146 views

### NDSolve solution violates initial conditions

I have the following code: ...
343 views

### How can I only draw outer common tangent to two circles?

I have code worked for drawing common tangent lines to two circles(http://en.wikipedia.org/wiki/Tangent_lines_to_circles), now I want to delete the inner common tangent lines, how? ...
275 views

### How to find the positive region of this function?

I'm new-ish to Mathematica and I'm using it to learn the basics of derivative trading (for fun not for trading!). I've defined a simple function to calculate the pay off of a trading on a call. I have ...
75 views

196 views

### Can't solve equation having complex coefficients

Why can't Mathematica solve $\quad\quad\frac{1-i}{\sqrt{2}}=e^{i \alpha } \tan \left(\frac{\beta }{2}\right)$ with the restrictions $\alpha \in [0, 2 \, \pi)$ and $\beta \in [0,\pi]$: ...
757 views

### How many times do the two given curves intersect at the origin?

I'm reading/studying on my own a book about algebraic curves. I'm trying to find a way for Mathematica help me with the following (the book, ISBN: 038731802X, allows me to use any CAS / program. ...
260 views

### Issue in ParallelTable after evaluating another function using NDSolve and FindRoot. What is wrong with this inverse?

I am trying to find the inverse of a function which is defined through NDSolve and NIntegrate. The question is pretty similar ...
109 views

### Already solved DE, now I need to rearrange and plot

I have solved for $z(w,x,y)$ in a differential equation: $$3\frac{\partial z}{\partial y} = 2(z-1) + (1-wy^2 )x$$ And I obtained the general solution: $z = f(w,x,y)$ Now putting in $x=0$, we have ...
82 views

### Solve simple differential equation - Error?

I get the error "The function Te appears with no arguments." when running this code. I'm not sure why. Is it because of the $Abs[\Gamma]$ ? ...
170 views

### Best way to determine polynomial coefficients in series expansion

I would like to solve the equation $$h'(\boldsymbol{x}_1)\left[B_1\boldsymbol{x}_1+g_1(\boldsymbol{x_1},h(\boldsymbol{x}_1))\right]=B_2h(\boldsymbol{x}_1)+g_2(\boldsymbol{x}_1,h(\boldsymbol{x}_1))$$ ...
183 views

### Could not solve a set of equations with available mathematica tools

The problem I described below is an simplified way of expressing it.(Sorry that I still did not figure out a way to copy the code to here.) The actual equation is like What I am trying to find is ...
164 views

### Solving a Trigonometric parameter

I have a similar case as given before : Solving a Trigonometric function with one parameter Let: m = 1; Dx = 100; ν = 0.25; b = 1; and, ...
133 views

### Quartic equation [closed]

After using Solve I am choosing the physical root of my equation and dealing further with this root. However, when I am changing parameters using Manipulate, I clearly see not smooth behaviour. Is ...
638 views

### Using Solve but getting no output

I am trying to solve a model using a constant-elasticity-of-substitution production function, but when I try to solve the first order conditions, I just keep getting back what I typed. ...
186 views

### Solving equations with QuantityVariable

I'm trying to understand how to easily solve equations that use QuantityVariable. Why does this fail? ...
57 views

### Resources/ best practices for exploratory economic theory work

This is a little general, so I will try to make it as specific as possible. I used Mathematica a fair amount to derive and check analytical solutions to problems in theoretical economics. Lots of ...
244 views

### How do I plot the differential of this function?

Suppose I have this function: $$z(x,y) = \left| \frac{ \frac{1}{3x +iy} -2x}{iy + \frac{1}{x}} \right|$$ I want the contour plot of $\frac{\partial z}{\partial x}$ with axes $(x,y)$. Tried this ...
98 views

So, I think the problem that Im having is simple but, still, Im not sure on how to do it. I have an equation with no analitical solution: $a_1 \sin \left(2 \theta \right)+a_2 \sin \left(2 ... 4answers 302 views ### How to extract only real solutions from the result of Solve For Example, I have the following polynomial equations: $$\left\{ \begin{array}{ll} \dfrac{2025 (208 x+5 (y-3446))}{52 (y+90)^2}+\dfrac{300 (8 x-21 y+1920) (y-80)}{7 (x+30)^3}+\frac{300 (80 x-21 ... 3answers 380 views ### Finding maximum value with position from Table of values I have this table of values, how do I find the maximum value? i.e. find z_{max}(x,y) ... 1answer 87 views ### Solving minimum length confidence interval problem I'm trying to find the minimum length of a confidence interval for the variance from a sample iid with normal distribution. I tried ... 2answers 388 views ### Solving the magic backyard puzzle with MMA I was trying to solve this puzzle using mma It looks like the generalization of the magic square. Anyway here my attempt:- There are four columns (x,y,z,w) and nine rowa which are denoted by the ... 0answers 37 views ### How can Mathematica solve 7 equations and want to find 7 variables [duplicate] I have 7 equations as below * e1 := (1 - a) p Subscript[A, 0] Subscript[s, K ] ! *SubsuperscriptBox[(s), (L), (-a)] = (1 - b) Subscript[B, 0] (1 - Subscript[s, K]) (1 - Subscript[s, ... 1answer 608 views ### How do I solve for one variable in terms of other variables in Mathematica? I'm fairly new to Mathematica, and I'm trying to solve a complicated equation with multiple variables. I've tried the following... ... 2answers 126 views ### Solving an Equation (Recursively) I have the following Values: a[0]=1;a[1]=0;a[2]=0;a[3]=0;a[4]=\frac{g_2}{20};a[5]=0. I need to compute the value of b[n] in the following equation$$a[n]=\sum _{m=0}^{n} (m-2) \;\;a[m] ... 1answer 112 views ### How do I solve for the real and complex parts of an equation simultaneously? If I were to have an equation, say something similar to... (1-Sqrt[x - I y])/(1+Sqrt[x - I y]) = A + I B Where I = Sqrt[-1], is there a way for Mathematica to ... 1answer 60 views ### Why can NSolve only solve this system of equations after trivial substitution? The first system immediately yields {}, but the second, equivalent, system yields the solution {{k -> 4.96048, tl1 -> 1.64842, tl2 -> 2.07466}} : ... 0answers 33 views ### What is that Root[…] inside the answer represent? [duplicate] So I am encountering this situation, in which mathematica doesn't give me the answer, but in a form of "Root". How do I interpret this ? what is the number after the "&" represent? How should I ... 0answers 108 views ### How to handle infeasible points in FindRoot? I am calling FindRoot[f[x,y],{{x,xInit,xMin,xMax},{y,yInit,yMin,yMax}}] where for some points {x,y}, ... 0answers 152 views ### Finding Roots of Non-linear Systems: Rescaling polynomials I'm trying to get all isolated finite equilibria of a moderate multi-dimensional non-linear system of equations. Particularly I have 9 independent variables and third order at most. It turns out that, ... 0answers 159 views ### NSolve for large models I'm a Mathematica rookie running version 7.0 for Mac OS X x86 (64-bit) (February 19, 2009) on a 2010 MacBook Pro. (I'm also a stackexchange "newbie" who originally posted this on stackoverflow, thus ... 1answer 144 views ### Simplifying a symbolic product of rational powers I'm trying to symbolically evaluate a lot of equations that can consist of up to 10 parameters. The form of these expressions is a product/quotient of rational powers of the mentioned parameters, ... 1answer 130 views ### Numerically Integrating to find a Maximum using NDSolve I am trying to numerically find an equilibrium (maximum) of a function using its differential. The following is a simplified version. ... 1answer 64 views ### Some question on “Reduce” Is this my mistake? I am trying to solve ... 1answer 72 views ### Finding linearly independent combination of vectors with a certain symmetry property I have two linearly independent vectors$v_1$and$v_2$. Is there a way for me using Mathematica to find two linear combinations$w_1$and$w_2$such that:$w_1$and$w_2\$ are linearly independent. ...
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I am currently trying to solve under what condition does the following term will be zero? ...