# Questions tagged [symbolic]

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

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### DSolve doesn't respond

So I am trying to use DSolve to solve the following system of equations: ...
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### Can Limit take limits of unknown functions?

For example, when I input this f[0] = 0; Limit[f[x], x -> 0] , it does not output 0. Is there a way to get it to output <...
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### Symbolically solving linear program [closed]

I have been surprised that Mathematica cannot solve a linear program. Specifically, I have tried to solve the following problem: ...
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### Solving partial differential equation

I am new to mathematica and I want to solve the following pde. I have two boundary conditions and one initial condition. I have tried the following code but the output is not the solution and it's ...
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### Problems with DSolve and NDSolve for Dirichlet problem on an annulus

To solve the Dirichlet problem on an annulus, I do the following in 12.2 on Windows 10 Pro ...
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### Normal ordering of operators multiplied by scalars

I have the following code for normal ordering of two Boson operators $a(x),\,b(y)$: ...
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### Extracting von Neumann neighbors from a list of lists [duplicate]

I want to be able to implement a rule that extracts the von Neumann neighbors from a given list of lists, that act as the entries of a rectangular matrix. Say a list of lists is given: ...
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### Creating a Symbolic Matrix

Probably very simple, but I don't know where to start with this. How do I go about creating a symbolic matrix, such as the one below? I want to be able to use this so that any list of lists that are ...
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### Expand product of symbolic sums (with identically named indices)

I have an expression that is a product of two symbolic sums. Sum[a[k], {k, 1, n}]*Sum[b[k], {k, 1, n}] How can I expand this expression? I want to see something ...
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### How reliable is AsymptoticIntegrate?

In new mathematica 12 there is a new function AsymptoticIntegrate. However, it seems that it gives me incorrect results in some cases. To be completely honest, it ...
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### NonCommutativeMultiply question- syntax question

if I define id as: id /: NonCommutativeMultiply[id, x_] := x id /: NonCommutativeMultiply[y_, id] := y then ...
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### Having problem in evaluating the eigenvalues of an $11\times11$ symmetric matrix in Mathematica [closed]

I am solving an $11\times11$ matrix in Mathematica. I am facing problem when I try to find the determinant or eigenvalues of this matrix. The error (Det::matsq/<...
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### Solve function used symbolic computation yields all the coefficients value zeros

I am trying to compute the symbolic coefficients of using Solve function. But this is yielding all the coefficients values zeros. What are the other ways to find ...
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### Can't compute the Integral

I tried to calculate an integral with the function Integrate, but it runs for a long long time without any answer. I have been checking the integrand and it seems ...
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### TensorExpand, TensorProduct and Distribution over Scalars

Consider: TensorExpand[( b1 x )\[TensorProduct] (b1 x + b2), Assumptions -> x ∈ Reals] (*x^2 b1\[TensorProduct]b1 + x b1\[TensorProduct]b2*) This works as ...
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### Solving Simultaneous equations of matrices

I am in a precarious situation where I have two equations: eq1 = α1 + αt12.t1 + αr11.r1 == 0; eq2 = γ1 + γt12.t1 + γr11.r1 == 0; Where each variable is a 3x3 ...
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### Table over array indices

I want to generalize the following table to a summation over $s[1], \ldots, s[N]$ and $t[1], \ldots t[N]$, where each variable sums over $\{-1, 1\}$. ...
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### A question on the exact value [closed]

Could anyone help me find the exact value of ...
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### How to define function in Mathematica

I have a 3 by 3 symbolic matrix M(x,y,z). Question:1 First, I want to find its eigenvalues and eigenvectors. After that I want to make each eigenvalue and eigenvector a function of x,y, and z i.e. <...
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### How to make calculations involving symbolic summation?

I want to minimize a function involving the sum of $n$ fixed (but indetermined) $x$ values, for example: Minimize[Sum[(x[i] - a)^2, {i, 1, n}], a] Expected answer: ...
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### Symbolic equation solving: Inverse functions are being used by Solve

I'm quite new to mathematica, so apologies if the question it soo trivial. I'm trying to symbolically solve an equation for R, and would like at the same time to mix in a second equation. What I've ...
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### Is there any formula to get the IRR from the slope of the Cumulative Cash Flow?

I've simulated a monthly regular cash flow with Excel, and the Internal Rate of Return (IRR) calculated from the first date to the current row. The curve of the IRR is very similar to the Transfer ...
163 views

### Trying to solve transient semi-infinite 1D Fick's Law with decay, getting constant for answer

I'm trying to find the solution to $$\frac{\partial f(x,t)}{\partial t} = a\frac{\partial^2 f(x,t)}{\partial x^2} - bf(x,t)$$ where $$f(0,t)=1, \lim_{x\to\infty}f(x,t)=0,f(x,0)=0.$$ I tried: ...
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### Why can't this simple second-order differential equation be solved?

I'm trying to solve the following partial differential equation: $$f(x,y) = \partial_x^2f(x,y)-\partial_y^2f(x,y)$$ for which one obvious solution would be: $$f(x,y)=e^{2x+\sqrt{3}y}$$ An even ...
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### Is substitution of symbolic expressions for JordanDecomposition correct?

Is it correct if I substitute letters A-Z for 25 expressions that are in a 5x5 matrix, run JordanDecomposition and then substitute expressions back? The process makes no progress after a day with ...
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### Trouble evaluating this definite integral, either directly or with indefinite + limits

I have the function  \Sigma(x) = \frac{\sqrt{R^2-x^2}(\left| R\right| -1)}{\left(R^2-1\right) \left(x^2-1\right)}+\frac{\tan ^{-1}\left(\frac{\sqrt{R^2-x^2}}{\sqrt{R^2 \left(1-x^2\right)}}\right)-\...