Linked Questions
14 questions linked to/from Replacing composite variables by a single variable
60
votes
4
answers
11k
views
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])
...
- 981
22
votes
7
answers
19k
views
How do I replace a variable in a polynomial?
How do I substitue z^2->x in the following polynomial z^4+z^2+4?
z^4+z^2+4 /. z^2->x
...
- 2,623
10
votes
3
answers
510
views
Matching (y/x)^u terms wherever the appear in an expression
Mathematica keeps rewriting expressions, so it is hard to figure what pattern to use.
I am trying to replace all occurrences of $\frac{y}{x}$ by $t$, but Mathematica re-writes $\frac{1}{\left(\frac{y}...
- 143k
9
votes
3
answers
3k
views
Replace expressions with symbols
First of all: I'm new to Mathematica, so I would appreciate it if the answers are quite complete.
I have the result of calculation that is expressed in $\sin$ and $\cos$. Now, all of these can be ...
- 983
8
votes
2
answers
274
views
Representing a value in an output as a self defined variable
I'm trying to find a way to have Mathematica always represent a numerical value as a self defined variable that I define using lhs=rhs. For example, if I execute
<...
- 213
5
votes
2
answers
612
views
Why is an integer not considered as a real?
Please consider the following:
zeros={0.,0};
data={1, 0., 0};
DeleteCases[data, #]&/@zeros
Head/@zeros
(*{Real, Integer}*)
(*{{1, 0}, {1, 0.}}*)
For my ...
- 4,361
3
votes
3
answers
640
views
Replacing a sum of expressions
I have an equation which Mathematica solves but gives a huge output. However I notice in this output that the same expression occurs many times. Namely:
$E=864 a^6 - 432 a^4 b^2 + 54 a^2 b^4 - b^6 + ...
- 147
2
votes
1
answer
165
views
Replace an expression with a slightly tricky LHS transformation
I would like to make the substitution x^(11*y) -> r in the following equation
x^(11 *y^z) - 1
to end up with:
...
- 473
2
votes
1
answer
1k
views
How to transform an expression using algebraical instead of pattern rules [duplicate]
I would like to transform rules algebraically. A very simple example would be: -
k^2 - 2 k x + x^2 /. {2*k -> 1}
This transforms to: -
$$k^2-2 k x+x^2$$
...
- 473
2
votes
1
answer
67
views
Algebraic replacement [duplicate]
How do I replace an algebraic expression with a symbol? I'm trying to replace repeated terms such as $(a+b)$ with c, for example, so that $x(4a + 4b) + x^2(6a + 6b)$ becomes $x4c + x^26c$ .
1
vote
2
answers
99
views
Applying a simple transformation rule when Plus automatically simplifies
I have the following simple rules:
{x2-x1->s1,
-(x2-x1)->-s1,
x3-x2->s2,
-(x3-x2)->-s2}
I want to apply that rule to the following:
...
- 25
1
vote
0
answers
39
views
replacement rules don't account for signs [duplicate]
I would like to make a single replacement rule that disregards the sign. I have the following expression:
...
0
votes
1
answer
278
views
simplification rule with symmetry
What rule can you think of to replace the first line by the second?
I have a bunch of expression like these, which I would like to simplify. All dependent cross terms must be written in the same ...
- 7,757
0
votes
0
answers
54
views
How do you make basic substitutions in Mathematica? [duplicate]
I have an equation:
e == m*c^2 + (1/2)*c^2*m*v^2
$$e==m c^2 + \frac{1}{2}c^2\space m\space v^2$$
I need to remove the $v$ variable and replace it with $p$. I also ...
- 1,610