Questions tagged [symbolic]

For questions about symbolic computation, as opposed to numerical computations.

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49 views

Define some variables to be real within the whole notebook

I want to define some variables to be real within the whole notbook? How can I do this? In the following you can find my code. I think the last step will be computed in seconds when I tell mathematica ...
1
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1answer
163 views

On double summation with Mathematica

Today I wanted to evaluate this sum using Mathematica: $$f(a,b):=\sum_{(k,l)\in\mathbb{Z}^2,\ l\ne0}\frac{1}{(2 i k a \pi + l b) (2 i (k - l) a \pi + l b)}$$ ...
2
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2answers
89 views

Plotting solution to Differential Equation with separable variables [closed]

Got this differential equation $$y'=\frac{-x^2(y+1)}{y^2(x-1)}$$ If I try directly to DSolve it ...
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1answer
49 views

Extracting parts of symbolic expressions

I've searched around and found things that could help me only in cases that are simpler than the one I had in mind. I would like to extract polynomials from expressions that schematically look like $$...
12
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1answer
327 views

Symbolic integration of potential over a disc : branch cut problem?

Context I am trying to explore the geometry of a crystal made of irregular bubbles. See animation here. very vaguely in the spirit of this post (it is in fact motivated by cosmology and galaxy ...
1
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1answer
90 views

ODE which can be solved without parametrisation [closed]

I want to solve the following differential equation, which can be solved without parametrisation $\qquad y^2y'^2-2xyy'=x^2-2y^2$ I need the solution for my student research project. When I try to ...
4
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2answers
165 views

RSolve not reducing for a certain recurrence relation

I'm trying to use RSolve as follows to solve a recurrence relation: ...
1
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1answer
29 views

Why does the Symbol stringification operation appear to work with only single argument strings? [closed]

I'm trying to label my symbolic object's using Symbol Works as expected Symbol["M" <> ToString[5]] Output ...
7
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2answers
534 views

Symbolic Quaternion Multiplication

It is possible to do the symbolic multiplication $qq^*$ of a quaternion $q=a+bi+cj+dk$ by its conjugate $q^*=a-bi-cj-dk$ using Mathematica? It seems that Quaternion package only works with numeric ...
3
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1answer
98 views

Symbolic decomposition of a tensor given an assumption

I am relatively new to Mathematica. Suppose I have a matrix M = {{a^2, a b, 0}, {a b, b^2, 0}, {0, 0, 0}} How can I get Mathematica to decompose this into an ...
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1answer
70 views

Calculate angle between skew vectors

I want to use Mathematica to calculate the angle between two vectors (say a and b) that don't lie in the same plane. The vectors ...
4
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1answer
226 views

estimation of values using NMaximize over symbolic array entries

I'm trying to generate instances of a dataset that satisfy specific conditions, based on the following equation: Each of four non-zero terms (term 1, A; term 3, B; term 4, C; term 5, D) is a scalar. ...
1
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1answer
152 views

Save and use results of LinearSolve for symbolic large system (28 equations)

I need to solve system of 28 linear equations, for 28 variables, symbolicly. The coefficient matrix is sparse, and is composed from 8 parameters (symbols). After that I need to use 6 of the variables ...
1
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1answer
339 views

How to change the integral variable and integral upper/lower limit?

I am dealing with the symbolic operation of taking the antiderivative, e.g., Integrate[f, x] (where $f$ represents a complicated function which cannot return ...
6
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2answers
304 views

How do I verify a vector identity using Mathematica?

I am trying to verify well known Frenet–Serret formulas in general setting using Mathematica. I need to consider a general space curve $r(s)=(x(s),y(s),z(s))$ in $\mathbb{R}^3$ and define its unit ...
2
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2answers
148 views

Newbie PDE Question

I downloaded Mathematica trial in order to try to solve a PDE that Matlab symbolic couldn't handle. I don't know all the bells and whistles but going along with online documentation. I am trying to ...
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1answer
79 views

Mathematica can't solve system of equations but doesn't show error

I try to solve a system of equations: ...
2
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3answers
868 views

How to define constants in Mathematica like c1,c2,c3,…cn?

Manually defining the constants is tedious if the 'n' is large. how to do this?
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1answer
37 views

From algebraic symbols to symbolic functions

i have a code which gives an output of this kind: rrr=2*f+1; Now i define a simple function: f[x_]:=3*x+2; How should i do ...
8
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2answers
178 views

Issue with Upvalues

I want to introduce two variables (I call them EXt and EXtC, where "C" stands for complex conjugate) which would mimic the behavior of a phase of a complex number. For that, I use the following tags: ...
5
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2answers
156 views

Why is $\sum\limits_{k=1}^{100} 0.01 $ different than $\sum\limits_{k=1}^{100} \frac{1}{100}$?

Why does evalutating $\sum\limits_{k=1}^{100} 0.01$ not result in 1? What I get is 1.0000000000000007. I know that the number 0.01 in binary results in an infinite sequence of zeros and ones, which ...
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0answers
44 views

How can I simplify expressions correctly?

the final output of my code gives this expression which i call ttt: ...
1
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1answer
72 views

Substitution of expressions for the output

I have a code which gives this kind of output : W = Sum[v[j]*b[j], {j, 1, 3}]; AA = (v[1]*b[1] + v[2]*b[2] + v[3]*b[3])*2 + 3 ; I know that if i want to ...
2
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1answer
74 views

Unable to use `Solve` to solve simultaneous equations, or use `Maximize` for exact maximum solution

Mathematica has found that the maximum of the following function is negative using NMaximize, but I am trying to prove that the maximum is negative (i.e. that the ...
3
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2answers
176 views

Transferring DownValues

I have a code in which I define something like this: cc[1, 2] = 1; cc[2, 6] = 12; cc[3, 7] = 3; After some manipulation I define a sort of temporary variable ...
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0answers
71 views

Parametric minimization running forever

I am trying to solve for the minimum distance between a line and a cone, for all possible lines in 3D space. I've formulated this as a call to Minimize, but it ...
2
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1answer
83 views

Reassign a value to an array element

I have a very complex code in which I assign a value to an element of an array and then I reassign to it another one. A minimal example: ...
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1answer
45 views

Setting to zero non defined array variables

I have a situation like this (for example): ...
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1answer
179 views

Simplifying a Sum of Fractions by Removing Fractions in Denominators

I have a sum of fractions of the form $x1 - \frac{(x2 + x3)}{(x4 + x5)} - \frac{(x6 + \frac{x7}{x13})}{(x8 - x9 - \frac{x10}{(x11 + x12)})}.$ How might I simplify it to remove fractions from the ...
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1answer
65 views

Evaluating the 1st argument of Set

I want to assign a certain value to an element of a tensor. This element is identified by an array obtained from some evaluations, so we fix it. Here i present an oversimplified core part of my code: ...
1
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1answer
467 views

Tag Times in Null is Protected [closed]

I've some problems with the error mentioned in the title. Unfortunately, my code is full of subscripts so I'll show it in a photo. In this code the central aspect is to assign a scalar value to an ...
1
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1answer
39 views

Strange thing about simplification between product and productory [closed]

Good morning, I have this strange problem. I have to divide a product of 5 variables by 4 of the 5 variables : $C x_1 * x_2* x_3 *x_4 / (x_1 * x_2* x_3 *x_4)$. Now if I do this I don't obtain only $C$...
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1answer
77 views

Position for array

how does Positionwork for array? In particular if i have something like this: ...
2
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2answers
64 views

Symbolic reduce of augmented matrices with TensorReduce

I am trying to reduce a symbolic matrix expression containing augmented/concatenated matrices using TensorReduce, but it does not behave as expected when transposing an augmented matrix. I assume the ...
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1answer
85 views

Conditions on parameters in Reduce

i have a system of equations in which there are two parameters F, G. I choose F,G positive. the code is: ...
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1answer
44 views

Defining a function on the difference of two inputs

Sorry if this is already on this forum somewhere, I had a look but couldn't find anything. Anyway, I am looking to define a function where the inputs are: a and <...
1
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1answer
178 views

DiracDelta convergence in 3D - Cartesian vs. spherical coordinates

Integrating DiracDelta in 3D in Cartesian coordinates works just fine i.e. gives vecf[{x, y, z}] ...
1
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1answer
104 views

Why the DSolve stop responding when they solve the system of coupled three differential equations?

I try to solve a system of six couple linear PDF. I applied the Laplace transform method and with some simplifications I retain with the following three coupled ODE ...
2
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1answer
51 views

How to declare derivatives of a multivariable function as real in order to get Re and Im part of the expression?

Re and Im work properly, with appropriate assumptions, in the example like this ...
3
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1answer
66 views

AsymptoticIntegrate with multiple integration variables?

I wanted to find the asymptotic form of $$\int_0^1\mathrm{d}x\int_0^1\mathrm{d}y\,\mathrm{e}^{M(x-1/2)^2+M(y-1/2)^2}$$ for $M\rightarrow\infty$. I tried ...
8
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2answers
94 views

Finding sub-expressions that simplify larger formula

If I use FullSimplify on a large formula it will consequently return a much smaller expression. However, suppose I notice the simplified expression can benefit from ...
7
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2answers
355 views

Evaluate Only Part of a Function

I have a list of functions, each containing none or more of the functions Plus, Times, ...
3
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1answer
143 views

differential equation solution with DSolve

I have a problem for my work, I need to calculate this diff. equation I have, ...
1
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1answer
105 views

Replacing one of the integrals in the multiple integral with an analytical solution

Problem consist in simplifying complicated multiple numerical integral, where I know analytical solution for a subset of them. Integrand is of the form ...
3
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1answer
328 views

Analytically solving of two coupled second order nonlinear ODEs

I have two coupled non linear second order differential equation. ...
2
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1answer
111 views

Fourier Transform of a symbolic expression

Hello I would like to do the Fourier Transform of H1'[t - L2[t]/c - L2primo[t]/c] I know that its transform has to be: ...
1
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0answers
67 views

Finding symbolic series coefficients

Is there any way to get the symbolic form of a series? For simple series this seems possible e.g. SeriesCoefficent[Exp[x],{x,0,n}] tells me that the general ...
5
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1answer
72 views

DiscretePlot Giving Incorrect Answer

I know similar questions have been asked before about bugs in Integrate, but I'm not sure what the particular problem is here (and whether or not there is indeed a bug). When I perform the integral: ...
5
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3answers
206 views

Power Function and Non Commutative Multiply

I'm trying to figure out the best way to define a Power function for non commutative multiply that retains some of the regular features of the ordinary power function. As of now, what I've been ...
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0answers
51 views

Add operator symbols to matrices in Wolfram [closed]

I am working with the matrices of the form $u = \begin{pmatrix}Y &y\\0 & Y\end{pmatrix}$, and I have an operator $a$ such that $au=\begin{pmatrix}Y & ay\\0 & Y\end{pmatrix}$. Since y ...