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

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40 views

Coupled ODEs with boundary conditions - DSolve Error

I'm relatively new to mathematica and I can't find the error here. I suspect it has something to do with the fact that vx, vy, vz aren't blue on my mathematica - as in, they already have some assigned ...
0
votes
1answer
99 views

Problems with Solve

I am having a problem similar to the previous question here. Solve either takes forever (I assume infinity) to run or returns an error. I have tried various combinations of using Round, Chop, N and ...
2
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3answers
135 views
18
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5answers
740 views

Fitting points to tilted, off-center ellipse

I have 24 x-y points that are supposed to form an ellipse. ...
0
votes
1answer
76 views

How can I speed up this multi-equation Solve problem?

I'm trying to solve a set of equations (chemical kinetics for a complex system, but don't worry about that). I ran it for 24 hours and I got no output. Here is the relatively simple code (I want to ...
1
vote
1answer
232 views

Solving a System of four equations (with logs) [closed]

I am trying to solve a system of four equations in four variables. I have read a number of threads on similar issues and tried to follow the suggestions. But I think it is a bit messy because of the ...
0
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0answers
82 views

To solve an equation

I am trying to solve the equation: Solve[Re[Integrate[(2 c - (r^2) Exp[- I 1.4746])^(0.5), {r, 0, 31.7576}]] == 2.1216, c] I want to integrate an expression in ...
2
votes
2answers
99 views

Extract desired solutions from Reduce

I have the function a = 1 - 3 Sin[theta]^2 Cos[phi]^2; which I solve for 'phi' when $a=0$ sol = Reduce[a == 0, phi] which ...
3
votes
2answers
412 views

How can I get the exact real solution of this equation?

I want to solve the equation Sqrt[x] + Sqrt[1 - x^2] == Sqrt[2 - 3 x - 4 x^2] with real solutions (in the real domain). I tried ...
3
votes
2answers
206 views

How to speed up minimization of function

I have the fallowing code (the functions within that code are replaced by simpler ones, but the code structure is identical): $$$$ ...
-1
votes
1answer
94 views

How to find these two intersections? [duplicate]

1.pv=(q1^2+q*^2-q3^2)/[2(q1+q*-q3)] q*=5.3415is the upper limit of q 2.pv+(1-2a)q+2F=2(1-a)C(q) at q=q1 and q=q3。 equation 2 is actually trying to find the intersections of two ...
0
votes
1answer
112 views

How to solve this nonlinear 2 by 2 equations?

I have a equation (x^2 + q1^2 - y^2)/2*(x + q1 - y) + (1 - 2*a)*q + 2*F = 2*(1 - a)*c[q] in q(variable) with parameters q1,a,F and function c(in variable q also, and I define it outside Solve so I can ...
4
votes
3answers
199 views

Why the inequality does not take into account the domain?

I have this inequality: Reduce[(4000-1000k)/(k-4) < 0] and the answer is k ∈ Reals I would expect ...
1
vote
1answer
75 views

FindRoot with vector functions

I'm trying to solve a system of non-linear equations with FindRoot, and I get the answer, but also a ...
0
votes
2answers
70 views

Solve prints message saying that it cannot solve my equation [closed]

I want to solve the fallowing equation: Solve[-(2/x^3) - 1/x^(5/2) - 1/x^2 + (4 Log[Sqrt[E] x])/x^3 == 0, x] Mathematica complaints: This system cannot be ...
1
vote
1answer
118 views

Unexpected result from FullSimplify

In the following simplification why doesn't Mathematica get a zero when asked to compute "Y-Z" eventually? ...
0
votes
1answer
79 views

wolfram mathematica intersection of two surfaces [duplicate]

I use wolfram mathematica. There is a function of two variables which defines the surface z = f(x,y), the second surface is defined as z = const. How to find the line of intersection of these two ...
2
votes
1answer
46 views

Solve[ ] for 2 variables not returning list of two variables

I type into mathematica: Solve[2 Sin[(Sqrt[3] x - 3 y)/2] == 2 Sin[(Sqrt[3] x + 3 y)/2], {x, y}] expecting it to return a list of pairs of solutions of the form ...
0
votes
1answer
61 views

Cannot solve equation

I just started using mathematica and I'm facing a problem that I just can't solve. I want to solve the following equation: Code: ...
1
vote
2answers
141 views

NSolve for high degree univariate polynomials

I am trying to solve a high degree univariate polynomial using Mathematica's NSolve command. But when I plug the solutions generated by Mathematica back to the equations, the equations are massive ...
0
votes
2answers
57 views

Solving a system with three equations and two variables [closed]

I am trying to solve some equations with two variables. This is the last step in the process of determining a x tilt angle of a molecule, as well its depolarization ...
1
vote
3answers
395 views

How can i get the solution of complicated equation?

This is the equation about zeta. NSolve[eq] could not solve this equation. (I think it is too complex to solve by NSolve.) I ...
0
votes
1answer
160 views

How can I obtain the complex root of an equation with FindRoot

I want to obtain the complex roots of some equations that are similar,but each of them has a different condition. this difference is the value of α in these ...
0
votes
0answers
70 views

NIntegrate: integrand has evaluated to non numerical values

I have pasted a code that has been giving me some trouble and errors when I try to compute. ERROR: "The integrand 1435.1232 E^(-6.4703566*10^6 s^2) deEntrance[s,phi]^2 has evaluated to ...
0
votes
1answer
98 views

Two questions on strategies for quantifier elimination

With the help of people here I was able to solve several cases similar to IC3 but this case - unlike the other cases - does not return an answer. I will try to run it for a day with 8 processors but ...
0
votes
2answers
146 views

Solving a system of equations using matrix form

Please bear with me as I am a beginner at Mathematica. In the following system, all variables on the right hand side are known, except for w1, ...
1
vote
1answer
114 views

Find all roots in the interval of nonlinear equation

I am struggling on how to find all the roots of 1+1/2^x+1/3^x==0 which lie in a given of real and imaginary interval. Solve ...
-3
votes
1answer
64 views

Finding integral bounds

i have this integral shown below is equal to 1, and i need to find "a" on mathematica, but I'm not sure how. integral (from 0 to a) sqrt((-50.8938 sin(8.4823 t))^2+(4-11.3097 sin(11.3097 t))^2) dt = ...
0
votes
0answers
75 views
2
votes
2answers
283 views

Solving simultaneous exponential equations

In[1]: Solve[{(1 + k)^n == 0.6, (1 + k)^(n + 1) == 0.3}, {n, k}] Solve::ifun: Inverse functions are being used by Solve, so some solutions may not be found; ...
0
votes
1answer
38 views

Using NDSolve with coupled ODE [closed]

I am trying to solve a simple coupled ODE in Mathematica but an error keeps on popping. I am very new to Mathematica. ...
2
votes
1answer
351 views

Solution given by Wolfram Alpha but not _Mathematica_

Why will Mathematica not give a soluion to Solve[Log[x] == Log[j, Log[j, x]], j], but Wolfram Alpha will?
3
votes
1answer
147 views

Control over the way matrix is displayed

I am wondering how to change the output format in Mathematica. For example, I have $x=\binom{3}{1}$ and $y=\binom{2}{5}$, and I want to find what linear combination of $x$ and $y$ produces ...
0
votes
3answers
173 views

Solving One Equation with Two Variables

I am trying to solve an equation with two variables. It is the last step in the process of using the method of undetermined coefficients to solve a nonhomogeneous differential equation. The equation ...
0
votes
1answer
80 views

NSolve cannot find the solution

I have some data which looks like: ...
0
votes
1answer
55 views

Inequality test returned unevaluated

I tried, Refine[Sin[k]^2/(k^2 + k + 1) < 1/(k^2), Element[k, Integers]] $\frac{\text{Sin}[k]^2}{1+k+k^2}<\frac{1}{k^2}$ It returns unevaluated. I ...
0
votes
0answers
47 views

Code for solving numerically an integro-differential equation

First of all, I want to greet the community. This is my first question, but I hope I will be able to help answering others members questions, although I am quite new working with Mathematica. I would ...
1
vote
0answers
33 views

Determine Functions Given Data Points [duplicate]

Is it possible for Mathematica to solve for f(x,y) = 0 such that {x,y} contains {{0,0.5}, {1,0.5}, {0.6,0.8}, {0.4,0.2}} ? Do we need to specify f(x,y) first ? ...
0
votes
2answers
148 views

find the real root

I have the following equation: \begin{equation} (y-1)^{b1} - C~~ y~~ \exp(a x)=0 \end{equation} where $a, b$ are real constants, $C$ may be a complex number. I need to find the real solution of the ...
0
votes
1answer
79 views

Solving a system of equations with variable coefficients

I am trying to solve a system of equation which seems to be simple but much as I tried I couldn't solve it in Mathematica and it says the coefficients need to be exact. Now, I was wondering if someone ...
-1
votes
2answers
46 views

single root of a cubic function

As it can be shown that the function f(x)=3x^3-9x+1 has a single root in the interval abierto (0,1). Try to solve using Newton Raphson method, but that is more than a demonstration calculation
0
votes
1answer
174 views

How to use `FindRoot` to solve an equation containing a parameter?

I'm trying to derive some of the results of the following paper: Electrodynamics of semiconductor-coated noble metal nanoshells, JT Manassah - Physical Review A In the paper there is matrix $\mathbf ...
1
vote
1answer
130 views

How to solve a complicated equation system

I am trying to solve the equation system eq1==eq2 for $\sigma1$ and $\sigma2$ where eq1 and ...
0
votes
1answer
57 views

FindRoot finds a solution not found by NSolve

I am trying to solve a polynomial equation of higher order with non-integer exponents. When the order of the system is greater than 4, FindRoot provides a correct solution that is not found by NSolve. ...
3
votes
3answers
154 views

How can I find the boundary function in RegionPlot?

I have a problem with finding the function that gives the boundary curve in RegionPlot comamnd. I use the following code to make the regions in which two ...
6
votes
5answers
4k views

How to get rid of warnings when using Solve on an equation with inexact coefficients?

When I solve this equation in Mathematica 8, I can get the right answer, but with some uncomfortable warnings. Equation: ...
2
votes
1answer
101 views

Finding the roots of a function with a parameter

I am using a differential equation method for finding the roots of a function. My function is much more complicated but I can illustrate my problem with a trivial example. The problem occurs when ...
0
votes
1answer
113 views

Finding the first five eigenvectors and values for a 500×500 matrix

I'm trying to find the first five eigenvalues and vectors of a matrix that has the following proporties: ...
6
votes
2answers
292 views

Why does Equal[“string”, False] not evaluate to False?

Why does Equal["string", False] not evaluate to False? I would have thought Mathematica could prove that these two things are ...