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

1
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1answer
50 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
200 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
63 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
39 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
264 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
108 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
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1answer
71 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
385 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
29 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
159 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
106 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
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0answers
36 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
18 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
45 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
171 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
69 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
53 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
43 views

Setting to zero non defined array variables

I have a situation like this (for example): ...
0
votes
0answers
15 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
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1answer
51 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
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1answer
60 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
105 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
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1answer
61 views

Position for array

how does Positionwork for array? In particular if i have something like this: ...
2
votes
2answers
37 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
29 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: ...
0
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1answer
42 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
vote
1answer
128 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
vote
1answer
91 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
votes
1answer
37 views
3
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1answer
51 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 ...
7
votes
2answers
69 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
votes
2answers
323 views

Evaluate Only Part of a Function

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

differential equation solution with DSolve

I have a problem for my work, I need to calculate this diff. equation I have, ...
1
vote
1answer
48 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
votes
1answer
120 views

Analytically solving of two coupled second order nonlinear ODEs

I have two coupled non linear second order differential equation. ...
2
votes
1answer
52 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
44 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
votes
1answer
61 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: ...
4
votes
2answers
88 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 ...
1
vote
0answers
42 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 ...
2
votes
1answer
39 views

Creating a function that differentiates rational functions

I want to create my own differentiation function Derivada. So, I already set some properties like: ...
7
votes
2answers
93 views

Mathematica Not Interpreting Free Parameters Correctly

Forgive me if this has an obvious answer, but I've run into seemingly the same problem in a few different contexts now. When I evaluate expressions using different variables, all of which show up as ...
3
votes
2answers
47 views

Using Symbolize to Convert Multiple Variables at Once

So, I have created a list of subscripted and overdotted variables that I would like to symbolize, so I run them through a for loop. Seems to me that this would work? Any help is appreciated. ...
1
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0answers
42 views

Symbolic differentiation on a function of matrices and vectors

Let $I_t$, $I$, $V$, $Z$ be vectors and $R$, $B$, $P$, $A$, $\mathcal{K}$, $\mathcal{P}$ be some matrices such that $$ \begin{eqnarray} S&=&-(R I+B^\top V)^\top \mathcal{R}(R I+B^\top V) ...
1
vote
1answer
91 views

How can I solve a certain complicated second-order PDE?

I am trying to solve the following complicated second-order PDE ...
5
votes
3answers
180 views

Factor polynomial of degree n+3

I'm considering a polynom poly[n,v] in v ...
2
votes
1answer
44 views

Maximize with matrices

How do I use maximise with an arbitrary sized symbolic matrix? e.g for a small matrix it is fine to write it out, ...
0
votes
2answers
64 views

Numerical solution of complicated trigonometric equation

I have the following equation to numerically solve for \[CurlyPhi] as function of $k$ and $x$. $k$ is normally between $-\pi\leq k\leq\pi$. ...
1
vote
1answer
62 views

Symbolically solving a complicated trigonometric equation

I want to solve a trigonometric equation involving a few sine functions, for an argument of sine function. The equation in its ...