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Questions tagged [symbolic]

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

0
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1answer
58 views

Taking derivative of general order

How can I directly evaluate the following derivative? $$ \frac{\partial ^n}{\partial x^n}\bigg[\sum_{k=1}^{m} (m-k)! (ax+b)^k\bigg] = \sum_{k=1}^{m} (m-k)! \bigg[\frac{k!}{(k-n)!}a^n (ax+b)^{...
0
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0answers
33 views

OpenCL for symbolic matrix manipulations [on hold]

I want to calculate a matrix multiplication of matrices with a size of 500 for example, but all elements are symbolic. Since it is a bit slow with a normal way, and gets slower and slower with ...
1
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1answer
69 views

How to distribute rules?

For example i want to have following equation : Det[A B C]=Det[A] Det[B] Det[C] What is the simplest way to distribute automatically?
6
votes
4answers
307 views

What is wrong with my approach to solving a heat transfer PDE?

I wanna solve the following heat transfer PDE using Mathematica. $\qquad u_{xx}=u_{t}$ with following conditions: $\qquad \begin{cases}u(x,0)=sin(x) &0<x<\pi &,t>0\\u_{x}(0,t)=1\\...
2
votes
1answer
35 views

Collecting w.r.t. long expression

Sorry for a probably naive question. I have the following expression ...
4
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1answer
136 views

why this PDE causes internal 1/0 division?

Assigned WRI Case number 4210941 Using 11.3 on widnows 10, this input ...
0
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0answers
57 views

How to sum over the variable in partial derivative operator?

I need to use the partial derivative operator in Wolfram Mathematica within a summation, specifically to define the D'Alembertian operator of scalar fields. I am having trouble summing over the D ...
0
votes
1answer
41 views

Characteristic Function of 2D Gaussian with Boole

Context Given the Probability Distribution ...
5
votes
1answer
87 views

Symbolic Neural Networks in Mathematica

Mathematica is very well known about its symbolic capabilities/functionality. Heavy users usually say that “everything is a symbolic expression”. Does this principle applies to neural networks? If ...
0
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1answer
43 views

FindRoot and symbolic evaluation

Following the Symbolic evaluation documentation, I am trying to solve the equation: $y'(x) = a*y(x), \quad y(0)=1$ where I later fix a via FindRoot, requiring that $y(2) = 2$: ...
1
vote
3answers
81 views

Evaluating complicated limits correctly

Let's say I have defined some function: a[x_] = x^2 Log[x^2]. If I try to evaluate a[0] Mathematica will complain that it is ...
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0answers
58 views
1
vote
1answer
64 views

solving coupled pde with conditions

I have two coupled PDE ...
1
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0answers
68 views

Finding root of symbolic function

I'm trying to find a root of the following equation $$\theta^\frac{t}{s}-\theta-\sqrt{1-p},$$ where $0<t\leq1\leq s$ and $0<p<1$. I've tried FindRoot and Reduce, but somehow they don't ...
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0answers
33 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
126 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
votes
2answers
68 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 ...
1
vote
1answer
41 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 $$...
11
votes
1answer
300 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
vote
1answer
85 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
votes
2answers
80 views

RSolve not reducing for a certain recurrence relation

I'm trying to use RSolve as follows to solve a recurrence relation: ...
1
vote
1answer
28 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
votes
2answers
429 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
votes
1answer
75 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 ...
1
vote
1answer
59 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
votes
1answer
215 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
vote
1answer
90 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
vote
1answer
46 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
votes
2answers
274 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
votes
2answers
119 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 ...
0
votes
1answer
74 views

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

I try to solve a system of equations: ...
2
votes
3answers
442 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?
1
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1answer
30 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 ...
7
votes
2answers
165 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
votes
2answers
121 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 ...
0
votes
0answers
37 views

How can I simplify expressions correctly?

the final output of my code gives this expression which i call ttt: ...
1
vote
1answer
24 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
votes
1answer
48 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
votes
2answers
172 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 ...
0
votes
0answers
70 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
votes
1answer
58 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: ...
1
vote
1answer
44 views

Setting to zero non defined array variables

I have a situation like this (for example): ...
0
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0answers
20 views

Using RegionPlot with NIntegrate causes symbolic evaluation when integrating

I am trying to plot the regions when a certain integral is positive. Because the function has many parameters I am passing the values through two sets of rules, one containing the pair of values I ...
1
vote
1answer
56 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 ...
1
vote
1answer
62 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
vote
1answer
156 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
vote
1answer
38 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 $C$...
0
votes
1answer
64 views

Position for array

how does Positionwork for array? In particular if i have something like this: ...
2
votes
2answers
41 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 ...
0
votes
1answer
32 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: ...