# Tagged Questions

How to manipulate expressions structurally, not necessarily complying with the rules of algebra.

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### Reorganise expression as trigonometric polynomial

I have this expression (obtained with Expand): ...
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I have the following coming from a computation, $$h_1 (u,v,w) = \frac{1}{v}\partial_v g(u,v,w)$$ and in Mathematica I have different quantities in terms of $h_1$ and its derivatives like $\... 0answers 33 views ### How to solve a quadratic inequality containing parameters? I have the following inequality to solve for$R$in terms of$\delta$and$n$, with assumption that$n \geq 3$and$\delta>0$: $$-2 < 2 -\frac{16n\delta^{2}}{R^{2}\sin^{2}\frac{\pi}{n}} \left(... 0answers 34 views ### Gradient Descent's Update Rule for Multiparameter Functions I'm sure this has been answered before, but I haven't been able to find it. I'm trying to manually implement gradient descent for some function, f, with a vector of any length. I define the update ... 2answers 63 views ### How can I get the coordinates of a graphics primitive from a Graphics expression? For example I have square = Graphics[Polygon[{{0, 0} ,{0, 1}, {1, 1}, {1, 0}}]] What functions can I apply to sqaure to ... 0answers 80 views ### Bringing rational functions to canonical form I have a complicated expression, which among other things has stuff like functions of rational functions: expr = f[x/(-x^2 + y)] + f[-(x/(x^2 - y))] (* + ...*) ... 1answer 190 views ### How do I insert OwnValues inside a held expression without evaluating it? Here is a very long and complicated expression, which we abbreviate as a. I store it using SetDelayed because I want to perform ... 0answers 39 views ### How to invert an Elliptic function where the elliptic nome is a function of an independent variable? I have a Jacobian elliptic function as a function of two independent variables x and y. The elliptic parameter m=m(y), 0 \leq m \leq 1, is also a function of the variable y, and thus the ... 1answer 48 views ### Newline in code with MakeExpression I start with f[x]. In boxes, this is RowBox[{"f", "[", "x", "]"}]. I apply ... 1answer 72 views ### How can I access a variable using Position? I want to define a vector PosVec[a, b] dependent on the variables a and b of a matrix ... 2answers 90 views ### CoefficientList for exponentials terms I have a long expression with exponentials of variable t1. I need to create a list of the coefficients for each exponential. The problem seems to be that several ... 2answers 88 views ### Reading Cells or Boxes expression by expression Let's say we have a cell: (*newline*) (*newline*) Plot[ x, {x, 0, 1} ] (*newline*) Plot[x, {x, 0, 2}] How to read it expression by expression? ... 1answer 80 views ### Replace pattern for exponentials Ultimately, I want to replace every Exp[(const) w[i,j]] to T[i,j] and Exp[-(const) w[i,j]] to 1/T[i,j] in the following expression ... 3answers 157 views ### How to get the long logic expression with a terse method I have a long logic expression (x==2||x==3||x==4)&&(y==2||y==3||y==4)&&(z==2||z==3||z==4)&&(m==2||m==3||m==4) How to get it by a terse ... 0answers 50 views ### Force expression in certain form Is there a function in Mathematica to force an expression to be transformed into a given form. For example f[x] is a function of ... 2answers 117 views ### Efficiently strip off coefficients in front of variables? I am working with multivariate polynomials and need a very efficient way to decompose monomials into coefficients and pure monomials. for instance consider variables ... 0answers 71 views ### Can Mathematica reliably determine the equality of any two constructible numbers? A constructible number is any number which can be expressed with only natural numbers and the operators +, -, \times, /, \sqrt{} (square root only). Is Mathematica's ... 2answers 118 views ### How to extract the structure of relationships amongst variables in a system of equations? [closed] Mathematica being a CAS, I would have thought what I'm trying to do a natural task. But I have not been able to find any information on this in the Internet. Basically, I have a large collection of ... 2answers 147 views ### What is the Difference Between Rule (->) and RuleDelayed (:>)? I am new to Mathematica so this question may seem rudimentary. Sorry for that! :) I want to implement the well-known property of Kronecker's Delta$$\Sigma_{i=1}^{n} a_i \delta_{ij}=a_j,\quad 1 \le ... 1answer 55 views ### Error: Recursion Depth of 1024 Exceeded During Evaluation I wrote a function that exchanges integration and summation in an expression. ... 1answer 87 views ### Simplifying expressions Let's define a function$\Omega(x,y)$... 1answer 72 views ### Problems with Displaying Output for Summation Consider the following code. ... 1answer 79 views ### Deriving the Fourier Coefficients Formulas with a Manual Procedure I already know that there are built-in functions to compute the Fourier coefficients but I want to derive their formulas manually. In fact, I want to obtain the final well-known formulas for the ... 1answer 67 views ### Replacing terms in a sum according to a condition If I have a generic expression such as ... 2answers 69 views ### Creating Boolean expressions over a set of indexed variables I've read lots of examples here on how to set one matrix Equal to another, but how do you nest And and ... 1answer 140 views ### A weird issue with Interval[$MaxNumber]

From the Interval documentation: For approximate machine- or arbitrary-precision numbers x, Interval[x] yields an interval reflecting the uncertainty in x. <...
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### Express roots of quadratic equation in a specific form [closed]

By solving this equation, I got two roots as follows: Solve[1 + Subscript[a, 1]*s + Subscript[a, 2]*s^2 == 0, s] Is there a way to express it in the form below ...
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### Substituting a Value into an Expression

I am new to Mathematica so pardon me for the elementary question. Can some one kindly explain that what is happening in the simple code below? The With command ...
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### How can PowerExpand be made to evaluate the ArcTan form that takes two arguments?

Consider c = Cos[phi]; s = Sin[phi]; ArcTan[c, s] // PowerExpand ArcTan[s/c] // PowerExpand which yields ...
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### Extract all elements from a list that belong to a set or have a set element as an argument

EDIT: Added that I want to extract not only the variables from a specific set, but also functions involving variables from a specific set. Given the set ...
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### Rearranging dynamic equations

I'm deriving dynamic equations for a simple system, this is what I get: How can I rearrange these 2 equations into the form like this: My code is: ...
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### Separation of variables in an expression

I am looking for the function equivalent of Sympy's function: as_independent (*deps, **hint) in Mathematica. The function naively separates an expression into arguments that are not dependent on deps. ...
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### Numerator not recognized

Here is a set of simple equations ...
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### Is there a function in Mathematica which removes brackets wrapping an expression?

Is there a function in Mathematica which removes brackets from an expression? RemoveBrackets[ {3} ] 3 Note: inspired by @garej's answer to this question :...
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### How to efficiently find all combinations of the letters in an alphabet given a condition

Problem: I want to find all unique expressions with n number of terms that contain all the digits (or characters) in alphabet. ...
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### intermediate steps of simplification of algebraic expression without evaluation [closed]

I am using MMA do do some algebra and I need to do some simplification. For example, I have the following expression  x^2 \left( \frac{6 \left(2 c_1 x^6+c_2\right)}{x^4} \right)-x \left( 4 c_1 x^3-\...
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### What's the easiest way to remove overall factors from polynomials?

I have code that outputs polynomials (in #1) such as the ones below (note that the trailing Function character ...
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### Evaluation of Alternatives

I recently stumbled upon a few examples that suggest patterns containing Alternatives do not evaluate for individual alternatives. For example: ...
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### Simple grouping equations [closed]

I'm new in the Mathematica world. A very basic question. I have been using the command Eliminate on a set of equations as follow: ...
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### Display position of expression as Tooltip

How could we display the position of any sub expression in an expression using Tooltip? This would be useful for example in order to locate the position of an ...
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### Is it possible to match a sequence with multiple heads without using Condition

Suppose I have: expr = Times[2, a[x,r], a[y,1], c[z,0,0], d[w,m]]; If I want to match a sequence of expressions with the same head ...
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### Finding coefficient in expression

I have expressions like these: ...
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### Custom rules for expressions in export to HTML(Fragment)

ExportString[Grid[{{a, b}}], "HTMLFragment"] ...
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### Is there some way to implement automatic TimeSeries extrapolation or series continuation?

I am working with a large number of TimeSeries of irregular length. This means that if I sum them, or compute the mean, it cuts off at the terminus of the shortest ...