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

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1
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1answer
96 views

Solve differential equations with an initial condition in the form of a limit as $t\rightarrow \infty$

I want to solve the following differential equation with the initial condition This is known as the Bunch-Davies vacuum, and the above are equations (4.1) and (3.37) from this paper Here is ...
1
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1answer
57 views

System solution [closed]

How to solve this system using Mathematica. eq1 := xsin[y] - 3.5 cos[y] - 4.5; eq2 := -xcos[y] - 3.5 sin[y] + .4; Solve[eq1, eq2, {x, y}] This does not work.
2
votes
2answers
71 views

Finding zero of nonlinear simultaneous equations [closed]

I'm trying to find the zero of nonlinear simultaneous equations defined in myfun1 and myfun2: ...
2
votes
2answers
73 views

Integral equation solving

So there is this equation that I have to numerically solve for T: Q/(3nRT) = f(T/300) - f(T/77) Here Q = 920.364, n = 0.24, R = 8.314 while f is defined as the ...
1
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0answers
62 views

DSolve throws an error about Solve and returns unevaluated [duplicate]

I evaluate: DSolve[{2*y[x] + y'[x]^2 + a*x^b == 0}, y[x], x] During evaluation of In[26]:= Solve::ifun: Inverse functions are being used by Solve, so some ...
1
vote
3answers
147 views

NSolve or Solve or FindRoot

I need to solve this equation: A == M/(f d/2 (1 + Sqrt[1 - 3.53 (M/(b d^2 c))])) to find M, with: A = 0 to 19635 for intervals of 5 f = 500 d = 100 to 500 ...
0
votes
1answer
44 views

Solving a system of four equations [closed]

I'm trying to run this: ...
5
votes
2answers
99 views

Rewriting expression in terms of factor

I have two expressions: expr = (a - R)^2 (a + 2 R)/(2 R^3); factor = 1 - a^2/R^2; I would like to write expr in terms of ...
2
votes
1answer
76 views

Can not Solve FinancialDerivative for volatility

Although Solve can solve FinancialBond for an input parameter (e.g. par) given the price of a bond: ...
1
vote
1answer
107 views
0
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0answers
27 views

Solve does not give solutions to all variables [duplicate]

I have a beam with $n$ points and I have to find a numerical solution of the axial force using Finite difference method Here is my code ...
1
vote
1answer
76 views

DSolve to make the path of a ball in a rotating turntable

I have two equations from a analisys of the following situation. A ball starts to move from the center of a Turntable (rotating disk). I tried to solve these equations on Mathematica but the ...
3
votes
4answers
172 views

Find the minimum positive-integer value which meet the requirement

If the equation is Mod[515 Sum[10^(3 d), {d, 0, n}], 53] == 0 Then I can get the minimum positive-integer value of n. ...
4
votes
1answer
216 views

How to speed up calculation of this equation (FindRoot)

I have come up with the following functions, and I need to calculate a value, in order to have a condition valid. In my problem, all data are given, and I need to calculate variable l. I am using ...
4
votes
5answers
377 views

Solve for exponents

I have this problem that I"m trying to work out: Here's my attemp: me = 0.51109991 mp = 938.2723 mpe = mp/me Solve[(2^n)*(3^mm)*(\[Pi]^p) == mpe, {n, mm, p}] ...
0
votes
1answer
76 views

Solve exp(x) = x [closed]

I need help to solve the function Exp[x] = x. I tried using Solve but I got an error that told me to use ...
1
vote
0answers
56 views

How to solve Irrational equation in non radical form

I have a problem how to solve this irrational equation. It is important to note that it is not necessary to present roots in radical form (impossible). For me it is important to have roots in this ...
4
votes
0answers
66 views

Why does Mathematica gives a solution which is not in the domain of the cot function? [closed]

I've tried to solve the equation $\cot \theta = 2 \cot 2\theta$ with the command Reduce and Mathematica gave $\theta = n\pi$ as solution, with $n$ an integer. But ...
-1
votes
2answers
79 views

How can I make a command to write out the solution of the absolute value inequality?

I've written this source code, but I can't finish it yet. ...
3
votes
1answer
73 views

plotting after solve does not display anything

I'm quite new to Mathematica language, I am trying to figure out where I am making mistakes in Plotting a specific function that depends to other variables: I want to plot ...
0
votes
0answers
54 views

How can I make an amateur demonstration to solve absolute value equations and inequalities?

I would like to make a program which can solve absolute value equations and inequalities, but I'm a beginner of using the mathematica. I found amazing good demonstrations at the web-page of ...
3
votes
1answer
95 views

Unable to solve equation for a variable by any method

I am looking to solve for the value of r when the derivative of the expression ...
0
votes
0answers
39 views

Both Solve and FindRoot fail to solve my equation [duplicate]

I am trying to solve for r when the equation ...
1
vote
1answer
85 views

Solving trigonometric functions in Mathematica

I am new to Mathematica language and recently I had the need to solve the following equations with two variables, A and B: ...
0
votes
1answer
44 views

Using the Solve function [closed]

I am new to using Mathematica and am attempting to find the roots of a function using the Solve[] function. I can replace $f[x]$ within Solve[] with the actual function and it will work that way, but ...
1
vote
1answer
77 views

System of nonlinear equations

I am new at mathematica, and I am trying to solve the following system of four equations (f11==0 ,f12==0 , f13==0 , f14==0) under mathematica 10 , they depend on the real variables "alpha, beta, R and ...
1
vote
0answers
39 views

solving with numerical methods [closed]

Hi I would like to solve the equation below in Mathematica.Since I am a beginner I can not solve it with NSolve and Solve.I don't know why.Do you have any idea?! ...
4
votes
0answers
73 views

Improve Accuracy of FindRoot

This is a follow up question to an earlier questions I asked. The link is: Product of $N\ 2 \times 2$ matrices and subsequently solving an equation dependent on the product As I am new here, I am not ...
4
votes
0answers
104 views

Why does Solve work in v9.0.1 but not in v10.3.1

I want to solve the following DE $$ P'=k(M-P)P, P[0]=53.08, P[50]=23.192, P[100]=76.212.$$ The Mathematica command is ...
1
vote
0answers
43 views

How can I use x->Root outputs from Solve? [duplicate]

Do not understand the meaning of the output given by Mathematica to this equation: ...
1
vote
3answers
84 views

How to use Solve command? [closed]

I have written a code like follows: ...
1
vote
0answers
35 views

complex algebra with Solve function [closed]

I wanted to solve this complex expression for L, Solve[(1/(R + (1/Iwc)) + (1/(R + IwL)))^-1 == R, L] where I is sqrt(-1) and mathematica is out putting {}. Does ...
0
votes
0answers
64 views

Select positive elements from a list of solutions

I'm solving two equations with two unknowns ...
1
vote
1answer
52 views

Getting the conditions for equation to be solvable

I have a parametric equation to be solved, but I do not actually care for the solution. I only want to know the range of parameters for which the equation has a solution. Is there a way to get the ...
0
votes
0answers
136 views

Why is Mathematica not solving this equation?

Every time I am trying to solve this equation Mathematica is just not doing anything. First time is showed error as quantity is not quantified or something. But since then whenever I am trying to ...
1
vote
1answer
80 views

Having issue for solving a system with seven equations

I have a system with seven equations and three constrains. I tried to solve them using NSolve, but it takes forever without getting any result. Also, I tried it ...
1
vote
2answers
88 views

Closed form solution equations involving finite sums

I am a beginner in Mathematica, so take this into account. I could not find anything similar in the internet so far. I am trying to find a closed form solution for ...
2
votes
1answer
47 views

FindInstance skips solutions

I have an equation to compute the bit-error rate of a binary symmetric channel: $$P_{err}(n,p) = \sum_{k = \frac{n-1}{2} + 1}^n\binom n k p^k(1-p)^{n-k}$$ I then want to find the smallest ...
0
votes
0answers
96 views

Solving general system of equations

I want to find the closed form solution to a general system of equations. The number of equations and variables is C. How do I specify the system of equations? If ...
0
votes
1answer
126 views

Help on using Solve

I tried to use Solve to solve a set of nonlinear equations and got this error: Solve was unable to solve the system with inexact coefficients or the system ...
1
vote
1answer
70 views

Double arrow in the outcome

Does anyone know how do I get rid of one of the double part at the start of the outcome rh-> rh-> ...
4
votes
1answer
99 views

How to equate coefficient of two polynomials? [closed]

Given two polynomials, How can I equate coefficients of them in Mathematica? For instance a + b x + (c+d) x^2 + (e+f)x^3 == 0
2
votes
1answer
127 views

How to handle a special Neumann-like boundary condition in NDSolve?

How to solve the following nonlinear ODE with two algebraic equations and one boundary condition? ...
0
votes
0answers
59 views

Is this problem parametrically solvable or it can just be solved for specific $\sigma$ and $\theta$?

In order to solve This problem: What is the maximum value of coefficient fv with the constraint that the matrix is positive semi-definite?, I have used the following code (Determinant is computed by ...
0
votes
1answer
54 views

Multiple stopping constraints in NDSolve

I need to numerically solve several differential equations, with several constraints, like this : ...
0
votes
1answer
90 views

How to solve the following GR PDE?

Someone could help me for solving the following GR PDE? (this code do not work yet) ...
0
votes
1answer
53 views

Using Solve with Mod [closed]

I'm new to Mathematica, and it seems like what I'm doing should be a simple operation, but I can't seem to get it to work, or return the right result. I'm assuming I'm doing something fundamentally ...
3
votes
0answers
74 views

Low accuracy while solving a multi-variable equation numerically

My question is as following: I was trying to make a function Vs2[r] with two parameters fit a set of conditions. Vs2[r]: ...
2
votes
1answer
72 views

How to get the analytical solution of this equation set

There is a equation set: {2 x^2 + 49 - 7 x - 2 x Sqrt[x^2 + 49 - 7 x] Cos[rad] == (7 - x)^2, 2 x^2 + 49 - 7 x - 2 x Sqrt[x^2 + 49 - 7 x] Cos[rad + Pi/3] == 49} ...
0
votes
1answer
75 views

what do those signs #1, #1^2, #1^3, & mean here? [duplicate]

I have read common pitfalls page and the documentation page but I still don't understand what do those signs mean here? ...