# Tagged Questions

Questions on manipulating complicated expressions and making them look simpler using Simplify, FullSimplify and Reduce.

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### Can I simplify an expression into form which uses my own definitions?

This seems like a simple thing to do, but I couldn't find anything relevant from Mathematica documentation. So suppose I have an expression: a*b/(a + a*Cos[a/b]) ...
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### How to specify assumptions before evaluation?

If I request mathematica evaluate an integral for me, I'll often get a more general ConditionalExpression than I want. Example : ...
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### Common subexpression from two expressions

I am working with some unpleasantly tedious polynomials, which need to be manipulated in various ways (integrate with respect to some variable, differentiate with respect to another). Since these ...
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### Why does Simplify ignore an assumption?

Here is the example: Simplify[x + y, x + y == a] Simplify[x + y, x + y == 5] Mathematica 9 output: x+y 5 I expect the ...
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### Replacing gamma at half integers by double factorial

It is well-known that for any positive integer $n$ the equality $\Gamma(n+\frac12)=\sqrt\pi\,(2n-1)!!/2^n$ holds, where $!!$ stands for the double factorial. I am using ...
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I have a sum of exponentials that I'd like to simplify. The issue is when I use Simplify, Mathematica loves to factor out one exponential factor. See below: $$e^{-i ... 1answer 174 views ### Can't simplify Abs[a*Cos[x]]^2 Why doesn't FullSimplify[ Abs[a*Cos[x]]^2, Assumptions -> {{a, x} âˆˆ Reals}] simplify to (a*Cos[x])^2 but this query ... 2answers 204 views ### Rewriting one expression using a variable representing another expression [duplicate] I have two expressions: w1 = (a+b)/c^2; w2 = (a^3 + 3 a^2 b + 3 a b^2 + b^3)/c^6; How can I ask Mathematica to try to find an alternative expression for ... 3answers 420 views ### How to simplify the following trigonometry expression such that the number of used characters is minimal? How to simplify the following trigonometry expression such that the number of used characters is minimal? (13*Cos[t] - 5*Cos[2*t] - 2*Cos[3*t] - Cos[4*t])/4 The ... 1answer 126 views ### Simplify equations with pattern assumptions When simplifying an expression using Simplify[expr, assumptions], the assumptions has to be explicit. Is it possible to simplify an expression with pattern ... 1answer 117 views ### Format Preservation of FullSimplify on Indexed System of Autonomous Equations I currently have a large system autonomous differential equations. I've indexed a more managable dummy system of identical form, using Part to reference each ... 1answer 228 views ### Simplify vector expression - is there something like “Factor” for vectors, dot products etc.? I am looking for a way to simplify dot products etc. Here is a minimal example: Lets say I have two vectors a and b: Array[a,2] Array[b,2] Now I evaluate their ... 2answers 460 views ### How to simplify expressions containing derivatives Is there a way to reverse the application of derivative rules in order to simplify expressions including derivatives? e.g. in Mathematica code: Want to go from ... 1answer 308 views ### How can I see which transformations Simplify attempts? The documentation for Simplify[expr] says that it performs a sequence of algebraic and other transformations on expr, and returns the simplest form it finds. How can I see which transformations it ... 2answers 615 views ### Simplify assumes Boolean 1 and 0 in logical expressions Per this chat discussion and this previous question where I encountered the strange behaviour: ... 2answers 492 views ### Memory leak issues I am working with noncommuting objects and basically I am using Mathematica to sort large expressions by normal ordering and simplifying them. To this end, I first create an object called ... 1answer 291 views ### What is the proper way to verify that two expressions are equivalent? First of all, it appears to me that$$\left|\frac{1}{x} + x^2\right| \Leftrightarrow \frac{|1 + x^3|}{|x|}$$is true. I don't know why, but my attempt to verify it in Mathematica failed. ... 1answer 404 views ### how to simplify large expression with lots of special functions in it (BesselY, Hypergeometric, MeijerG etc…) I saw this DE in Maple forum. When solving it using Mathematica 9.01, even though the result was correct (both solutions gave the same numerical answer for some random values), Mathematica's answer ... 1answer 458 views ### Why doesn't FullSimplify get rid of the common factor in this expression? FullSimplify does not get rid of the z factor in the following expression: ... 1answer 265 views ### Why does Simplify with TimeConstraint return Removed[$$Failure]?

Bug existed in version 7 and is fixed in version 10.0.0 I have a rather ugly Mathematica expression (edit: shown below) that I would like to simplify with a time constraint; simplifying without a ...
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### Using FunctionExpand to evaluate symbolic derivatives

Some symbolic derivatives of certain special function are not expanded automatically, but FunctionExpand often helps to get a derivative-free closed form ...
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### Attaching persistent assumptions to symbol definition

Is it possible to attach assumptions to a symbol? This relates to this question. Most of my work involves physical equations, i.e. there are basic assumptions on variables that will always hold true ...
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### Unable to evaluate reasonable max expression

Consider the following statement: Max[0, Sqrt[1 - Cos[4 \[Theta]]]] You'll find that Mathematica won't evaluate this, because it doesn't know the range of ...
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### Shaping/simplifying equations in a certain way

A problem I am occasionally facing is to simplify an equation not to it's shortest form but to a form that is simple by other means. Often, this is grouping the term according to certain functions, ...
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### Behavior of Reduce with variables as domain

When using Reduce, I accidentally put a set of variables as the domain. To my surprise, it not only seems that Reduce expects ...