Questions tagged [simplifying-expressions]
Questions on manipulating complicated expressions and making them look simpler using Simplify, FullSimplify and Reduce.
388 questions
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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])
...
- 1,001
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votes
2
answers
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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 ...
- 1,243
32
votes
3
answers
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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 ...
- 421
21
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4
answers
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Complex number operations: telling Mathematica variables are real
I want to do Conjugate[a + b*I], but when I do that, the solution is
Conjugate[a] - I*Conjugate[b]; when for me, a and b are ...
- 211
11
votes
3
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Simplifying the derivative of $|x|$
Context
In[855]:= D[Abs[x], x] /. x -> 1
Out[855]= Derivative[1][Abs][1]
In[856]:= D[x, x] /. x -> 1
Out[856]= 1
Question
Why is ...
user1602
89
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6
answers
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Advice for Mathematica as Mathematician's Aid
I use Mathematica mainly as an aid in symbolic attacks on problems, usually intermediate or harder and often number theoretic. While Reduce, ...
- 993
17
votes
2
answers
18k
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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 :
...
- 6,518
23
votes
4
answers
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Factoring polynomials to factors involving complex coefficients
I've run into some problems using Factor on polynomials with complex coefficient factors. Reading the documentation it looks like it only factors over the ...
- 423
18
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2
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3k
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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 ...
- 1,762
30
votes
1
answer
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A one line proof that one is zero using Mathematica 10
a = (Sqrt[2] + 1) (Sqrt[2] - 1) - 1;
{a/a, Simplify[a]/a, b/b == Simplify[b]/b}
{1, 0, True}
This one line "proof" that one ...
11
votes
2
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2k
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Why aren't these additions of integrals and summations equal?
I have the following code:
Simplify[Integrate[f[x] + g[x], x] == Integrate[f[x], x] + Integrate[g[x], x]]
To test:
$$\int{\left(f(x) + g(x)\right)dx}=\int{f(x)...
- 1,171
31
votes
4
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FullSimplify wrongly reduces expression to zero
Bug introduced in 9.0 and persisting through 12.2
I get the following output with a fresh Mathematica (ver 10.0.2.0 on Mac) session
...
- 968
18
votes
1
answer
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How to prevent reduction of a fraction into lowest terms?
I have a question about the concept of simplification. I want to explain it with an example.
When I write the fraction $4/8$ in Mathematica, the output is
1/2.
How ...
- 757
10
votes
4
answers
910
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How do I invoke the default complexity function?
Documentation on ComplexityFunction says:
With the default setting ComplexityFunction->Automatic, forms are
ranked ...
- 6,611
15
votes
3
answers
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Combining cosine or sine terms into a single cosine or sine
A function that is the sum of two cosine terms of the same frequency
x[t_] := a1 Cos[w0 t + b1] + a2 Cos[w0 t + b2];
can be simplified to a single ...
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