Questions on the analytic and numeric equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).
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0answers
11 views
Statistics Question [migrated]
This is probably super simple to most of you on here, but I was chatted by a friend earlier with a question. It reads just like this:
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1
vote
0answers
42 views
Is this being simplified correctly? [closed]
I'm unsure if this is a bug or if it's a case of Mathematica not doing quite what I expect it to.
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5
votes
0answers
46 views
Faster way to perform SameQ[Reduce[…], Reduce[…]]
I'm have some expressions that I need to confirm the equality of. SameQ[Reduce[...], Reduce[...]] works like a charm for the more simple expressions, however when ...
3
votes
1answer
97 views
Solving an inequality that contains Log expressions
How can I solve the following inequality? I tried the command Reduce, but the computer is still computing it (c is an real number).
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1
vote
1answer
64 views
How to get a solution set of a nonlinear system of equations?
I'm trying to find the solution set of {x, y} variables for the following system of equations:
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3
votes
1answer
78 views
Cannot solve system of linear equation sums?
I cannot get mathematica to solve:
The problematic code:
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5
votes
2answers
200 views
Find all the integer numbers $a$, $b$, $c$, $d$, $e$, $f$, $k$ to this equation have three integer different solutions?
How to choose all integer numbers $a$, $b$, $c$, $d$, $e$, $f$, $k$ belongs to interval $[-10,10]$ to the equation $$\sqrt[3]{a x + b} +\sqrt[3]{c x + d} + \sqrt[3]{e x + f} =k$$ has three integer ...
8
votes
1answer
174 views
Efficient way to solve equal sums $x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k$ with Mathematica?
I need to solve the system of equations, call it $S_1$, in the integers
$$x_1x_2x_3x_4x_5 = y_1y_2y_3y_4y_5$$
$$x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k,\;\; k= 2,4,6$$
I used a very ...
1
vote
0answers
55 views
Bounds on random number
I have a Markov Chain Monte Carlo code that uses a chi squared function to fit some data.
I am running into an issue now with getting unrealistic values for some of the free parameters
in the code. ...
16
votes
1answer
298 views
The Orbit and Perigee of the Flamsteed comet
Historical context
This year we have the 330-th anniversary of the Battle of Vienna - one of the great formative events of European history, it took place on September 12, 1683.
Kara Mustafa, Grand ...
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0answers
40 views
Evaluating the different calculations
I am a new user. I wonder that either there is possible to evalute different calculations at the same time in Mathematica or not? Can i share the kernels for different calculation at same time?
2
votes
0answers
61 views
Reducing exponential inequalities fails
I am quite stumped by this problem :
Reduce[ N^(x-y) <1 && N > 0 , x, Reals]
gives the expected result
...
-1
votes
1answer
88 views
Solving for variables in a series of nonlinear equations [closed]
I have a nonlinear expression in five variables. I want to use Mathematica to solve for three of the variables. I have a series of points giving values of x an y and I am trying to solve for a,b, and ...
0
votes
0answers
71 views
draw a graph of a polynomial function with variables in the denominator [closed]
I have an equation f(u,z1,z2)=0, which is a long and complicated polynomial function with u in denominator.
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0
votes
0answers
44 views
Collect and factor equations with certain terms
Collect user defined terms from a symbolic algebraic expression
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4
votes
2answers
123 views
find where 3 inequalities are simultaneously greater than zero
I have 3 functions, f11[l], f12[l] and f13[l], and I would like to know for which values of l these 3 functions are greater than zero. How do I do it analytically or numerically or graphically in ...
1
vote
1answer
80 views
Prandtl-Meyer function
I'm trying to solve for Mach number based on the given Prandtl-Meyer function, however I keep getting odd error.
Here is my code:
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1
vote
0answers
83 views
I can't solve this set of equations
I am having trouble solving a set of equations in mathematica. I do not get any errors, but i don't get any answers as well.
I have some restrictions on my parameters and variables in the equations ...
4
votes
3answers
206 views
Solve for the intersection point of 3 surfaces
Basically, I have three 2-torus (tilted) in 3-dimensional Euclidean space. They are expressed by parametric equations:
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1
vote
2answers
99 views
Count and plot the number of solutions in an interval
I have equations depending on one or more parameters and I want to find and plot the regions in the parameters space in which there are a specific number of solutions.
For definiteness let's ...
1
vote
1answer
172 views
solving a cubic equation
I need to find the minimum $r$ and the maximum $k$ of the following cubic equation for which there does not exist three distinct real roots.
$rx^3-rkx^2+(r+k)x-rk=0$.
Is it possible to find such $r$ ...
1
vote
0answers
6 views
Identify the curve from the sample points [migrated]
I am writing a script which will identify the patterns drawn on the touch-pad of the laptop. I have generated all the points where user moved his finger over the touch-pad using synclient.
Now i ...
-5
votes
1answer
44 views
How can I solve this system with Mathematica? [closed]
Systems with 3 equations and 3 unknowns ...
The unknowns are {p,q,j}
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0
votes
1answer
121 views
How can I solve this nonlinear system with 3 equations and 3 unknown? [closed]
I have this system with 3 equations and 3 unknowns:
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0
votes
0answers
80 views
Solve equations real and imaginary part separately
For my system of equations, the procedure described in Solving complex equations of using Reduce works no more. How can I separate the real and imaginary part of ...
2
votes
1answer
63 views
Error/warning when using NSolve for simple equation
I am using NSolve to solve an equation, as shown here:
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2
votes
1answer
58 views
Finding the root of a nested function with small values
I have reduced an error in my program to this line of code:
FindRoot[Nest[# (1 - #) k &, 1/2, 2^4] - 1/2, {k, 3.5}]
It works for $2^1, 2^2, 2^3, 2^4,$ but ...
-3
votes
1answer
132 views
Symbolic Simulations
I have 9 nonlinear equations and 10 unknowns. It is not possible to obtain a numeric solution but I do get a parametric solution. It is useful in my case because I want to observe how parameters (p1, ...
3
votes
0answers
118 views
FindRoot gives a wrong solution which obviously should not be there
I got stuck on FindRoot and I didn't see any similar problem posted, so let me explain what I am trying to do and what problem I meet here.
I try to find roots of a particular function, which in the ...
0
votes
0answers
55 views
Exposing a variable [closed]
This is the basic equation
\[Sigma][T]=E^((-20.7302 + 0.0147986 T) x) (625.646 - 3.50008 T) x^(
1.03651 - 0.000739932 T)
Then there are commands:
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2
votes
0answers
111 views
Nest for large value of n
I am working on a problem to find the Feigenbaum constant. In this problem I have to get $f^{2^n}(1/2)$ with $f(x) = kx(1-x)$. I use Nest to get $f^{2^n}(1/2)$ but ...
2
votes
1answer
82 views
Solving a system of equations
Mathematica doesn't want to solve my exact system with 3 equations and 3 variables.
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7
votes
0answers
144 views
Creating and using an explicit piecewise function in a convenient way
I have a set of data points that define a function in the form
curvePts = {data1,data2,...}
where
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-4
votes
1answer
134 views
2
votes
1answer
89 views
A basic problem with Solve
I have this equation:
4b*Cos[2t]-4a*Sin[2t]==4Cos[2t]+8Sin[2t]
Which I would like to solve. Without using mathematica, you can pretty easily see that a = -2 and ...
3
votes
2answers
206 views
Mathematica does not understand (R^3)^(1/3) is the same as R [closed]
In the output from a calculation in mathematica stands a/((R^3*c)^(1/3)), with c and a ...
2
votes
0answers
75 views
Conditional statements in intial conditions?
This is potentially a daft question, but I thought I'd ask it; I have some material free to diffuse in a boundary between rn and ro; I've been able to get it working nicely for neumann type boundary ...
0
votes
0answers
77 views
Simultaneous Equation Solving Under Nonnegative and Bounding Conditions
I have nonlinear equations to solve parametrically;
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0
votes
1answer
125 views
solution of differential equation
I have the following code that gives you a phase portrait of a 2d system and I can't understand what means the 3rd and 4th line (sol1 and sol2).
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0
votes
1answer
49 views
Define variable relationships and dynamically update variables
I would like to define a relationship between 3 variables first and then later when I have filled two of the variables with a number, I would like to extract the value of the last value.
For example:
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0
votes
1answer
36 views
How to delete duplicate solutions of this system of equations?
I want to find vertices (has integer coordinates) of the triangle $ABC$ with the centorid is $G(1,1)$ and orthocenter is $H(3,3)$. I tried
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1
vote
1answer
117 views
Solving Intervals
In a recent question I posed, it was noted that by design, Sqrt[ blah] only returns the positive branch, even though we might want to obtain all possible symbolic solutions. So, taking care to avoid ...
5
votes
1answer
87 views
Why is FindInstance failing when I relax a set of constraints?
I'm attempting to use FindInstance to generate coordinate sets for plausible triangles with edge length distance constraints. E.g.:
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2
votes
1answer
141 views
How to solve this equation with integers as a solution?
I want to solve the equation $$x^y + y = y^x + x$$
with $x$, $y$ are integer numbers. I tried
Solve[x^y + y == y^x + x, {x, y}, Integers]
How to solve the ...
0
votes
0answers
51 views
DSolve::overdet for system of linear PDEs
I would like to resolve symbolically the following equation:
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4
votes
2answers
133 views
Using RSolve correctly
I am having problems persuading Mathematica to solve even the simplest recurrence relations. As an example, how would you do the following?
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0
votes
0answers
77 views
Defining and Solving Systems of Equations Using Matrix Tables
I've defined a system of equations, but I been unable to get Mathematica to solve for the individual variables created by matrix tables.
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1
vote
2answers
115 views
Using FindRoot with an interpolating function
This question bears resemblance to a few other questions on mathematica.SE about finding points of intersection of crossing curves. I know that the guidebook of numerics has an entry about the whole ...
5
votes
3answers
204 views
Solving a system of equations with conditions related to the number of solutions
The equation below describes a conic with oblique axis:
$$9 + 22 x + 9 x^2 + 46 y + 24 x y + 16 y^2=0$$
It is a parabola, as the coefficients in $x^2$, $y^2$, $xy$ form a perfect square. To find the ...
3
votes
1answer
75 views
Find point at which equation stops having roots (if it exists)
I am interested in the roots of this function:
f[M_, b_] := 1 - (2 M Gamma[2, 0, (1/M + b M)/Sqrt[b]])/(1/M + b M)
for fixed values of b. In particular I want ...
