Questions tagged [simplifying-expressions]
Questions on manipulating complicated expressions and making them look simpler using Simplify, FullSimplify and Reduce.
1,521
questions
2
votes
2answers
43 views
How to split the expressions into four parts include the coefficients of Sin[x], Cos[x], and Exp[x], respectively?
Given three expressiones as
...
0
votes
0answers
23 views
Vanishing with the derivative terms in perturbation theory
Following the question in here, now I would like to make the terms with derivatives to vanish. To shortly explain, given a variable decomposed as follows:
$a(t,r) = a(r) + \delta a(t,r)$
in my long ...
0
votes
0answers
28 views
3
votes
1answer
93 views
Strange behavior of `Apart`
Here is a piece of sad comedy based on some Apart behavior. Is there a way to make Apart do the expected step?
Consider a very ...
2
votes
2answers
84 views
Exponentiation with parentheses
Why doesn't the following always simplify to 0?
Simplify[a^(b c) - (a^b)^c]
If we Assume a...
1
vote
1answer
70 views
Assuming that only the 2nd order terms are zero
I am dealing with first-order perturbative theory, that is, any variable may be decomposed as
$a = a + \delta a$
and the same would occur with several different variables, let's say, $b$ and $c$. ...
1
vote
0answers
52 views
Assumptions with conditions
How does one specify the assumption that a function is real for real arguments?
Compare
Simplify[Re[I f[x]], Assumptions -> f[x_] ∈ Reals]
...
2
votes
2answers
145 views
Simplify appears to give different results
I have an issue with Simplify (and FullSimplify) giving a different numerical expression to the pre-Simplified expression. The function is an alternating sum of trigonometric quantities:
...
0
votes
0answers
32 views
Output of Reduce + Simplify
I'm using Reduce to solve some equations and then simplify to eliminate some undesired results. The problem is that, when I apply Simplify, it messes with my output from reduce.
As an example:
...
4
votes
1answer
97 views
Mathematica not simplifying rational powers in complex expressions
I have the following expressions and I would like to obtain a final result purely in the real domain.
...
8
votes
1answer
600 views
Correct way of simplifying the result of an integral
Many times Mathematica gives enormous results to simple problems. One uses the program more for trouble than for not knowing how to solve the problem.
As an ejemplo I present this integral that ...
0
votes
0answers
41 views
how to force TransformationFunctions
I have this function:
F[z_, y_, θ_] = Sqrt[3]/(2*π)*w^2/z^2 *
Exp[-w^2*(θ^2/z - 3*y*θ/z^2 + 3*y^2/z^3)]
I want to calculate
...
0
votes
1answer
32 views
Simplifying sums and showing equality - limitations?
Is it possible to verify the following lhs,rhs involving the sums
are equal, with Mathematica?
I can verify it for individual values of $d$ variable:
...
0
votes
1answer
30 views
Distribute dot and multiplication on a sum
I have a simple problem, I would like to get the following:
In= Distribute[a.(b+c)*d]
Out= a.b*d+a.c*d
Meaning that I would like the dot product and the ...
2
votes
0answers
47 views
How to remove the Riemann tensor derivatives using Bianchi identity?
For the third-order Lovelock gravity, after varying the Lagrangian versus the metric, I found some derivatives of the Riemann tensor which should not be appeared. How can I remove them? Maybe using ...
0
votes
0answers
39 views
How to get rid of these matrices?
I have divided a complicated Lagrangian to some separated terms to be able to Simplify it. The thing is, in the general case (non-divided Lagrangian) the problem is ...
0
votes
3answers
70 views
expression containing radicals of imaginary numbers
I can't bear an expression containing radicals of imaginary numbers,
in case it can be expressed as in terms of radicals of real numbers only.
For example, I can't bear the expression
Sqrt[2 + i]
...
3
votes
1answer
50 views
Simplifying symbolic expression with Heaviside step function
When inputing
Integrate[HeavisideTheta[s - t], {s, 0, 1}, Assumptions -> {t > 0}]
Mathematica correctly simplifies if to
-(-1 + t) HeavisideTheta[1 - ...
6
votes
3answers
496 views
Factoring the square of this polynomial?
I have a polynomial $$\frac{b^4}{a^4}-\frac{2 b^2}{a^2}+1$$ and I want to complete the square to get this kind of expression: $$\left(1-\frac{b^2}{a^2}\right)^2.$$
I had try:
...
4
votes
1answer
171 views
How can I change Simplify
I have an application where I strongly prefer $1+\frac{3}{2+3x}$ over $\frac{5+3x}{2+3x}$, and $\sin(2x)$ over $2\sin(x)\cos(x)$. In general, I prefer to minimize the number of occurrences of the ...
2
votes
1answer
61 views
Solving 2D convection-conduction equation via using Fourier integral transform: the disappearance of the convection term?(with code)
I am currently solving a 2D convection-conduction equation. The convection is only working on the x direction. The governing equation and its associated conditions are given as
where T is the ...
2
votes
0answers
75 views
Expression manipulation
How can one write $\frac{ad+bc}{bd}$ in $\frac{a}{b}+\frac{c}{d}$ form? In other words, is there something opposite of Together[]?
Edit
My intend was to write
<...
0
votes
1answer
57 views
WolframScript not simplifying output
I'm trying to multiply a matrix and a vector (imported from a csv) in Wolframscript to speed up a process normally done with Mathematica notebooks. This is my first time using Wolframscript, however, ...
3
votes
3answers
73 views
Identify complex expression and replace
I'm having trouble finding a way (if there is) to analyse an expression, identify a complex pattern in it and then replace it with another thing. I think it will be easier to explain my problem with ...
0
votes
1answer
61 views
How to simplify an expression with no constraints?
Simplifying expressions on Mathematica is a recurrent topic. However I found myself stuck with this one:
Solving an rational equation on Mathematica gives me the following expression:
...
1
vote
1answer
38 views
Implementing global Assumptions [closed]
Why do the following commands
$Assumptions = {Element[x, Reals], x > 0};
Solve[{x^2 == 1}, {x}]
Solve[{x^2 == -1}, {x}]
give
...
0
votes
0answers
27 views
Completely expand and simplify logical expressions?
Consider a logical expression such as
expr = (a == b + q - w || c == d) && (q + c - d == w || e == r);
I wonder if there is a function that would ...
3
votes
0answers
33 views
How to speed up xTensor simplification?
I need to compute a variation of the 4th rang symmetric tensor. I've written a code that successfully computes it, but when I use the resulting tensor to compute the second variation the ...
0
votes
2answers
43 views
FullSimplify not finding trig substitution with other terms present
Consider the following:
FullSimplify[Cos[x - y - z] + Cos[x + y + z] + 1]
Mathematica simply returns the exact expression with no simplification. However, if I ...
7
votes
2answers
86 views
Fullsimplify output depends on variable order
Bug introduced in 5.2 or earlier and persisting through 12.0 or later
Mathematica 11.3.0.0 (used on a Mac) seems to give different results when using FullSimplify. ...
5
votes
1answer
79 views
Make assumption for function with variable argument
I would like to assume that a>t[b_] for any b, such that e.g. Simplify[a>t[c]]==True. ...
0
votes
2answers
44 views
0
votes
0answers
46 views
Convert Part of an Expression Using ExpToTrig
I'm wondering if there's a nice way to convert only parts of an expression, say exponential functions of varible $\theta$ to trig. The motivation is best descripbed by the following example.
...
0
votes
0answers
70 views
Time spent on a transformation exceeded 300 when solving the optimization problem
I have the code which shows below to solve an optimization problem, but it will show that it's over the time constraint of 300 seconds. Is there anyone who could help me solve it. Thanks.
...
0
votes
0answers
57 views
0
votes
3answers
81 views
How to simplify a three variables expression with Simplify?
I want to calculate the value of $\nabla\cdot\frac{1}{(x^2+y^2+z^2)^{1.5}}(x\hat{x}+y\hat{y}+z\hat{z})$. I used the following syntax:
...
2
votes
1answer
69 views
How do I force this simplification?
I am trying to calculate:$$\epsilon_{ijk}n^iM1^j\epsilon^{lmk}n_lM2_m$$
Defining the vectors as:
M1={M1x,M1y,M1z}
M2={M2x,M2y,M2z}
n={nx,ny,nz}
and using
...
0
votes
0answers
23 views
Optimizing and Parallel Computing for Large Dyadic Intervals
I need help with the efficiency of my code i.e. less time so I can compute for large range of values.
My function n[x] takes in a number x and outputs the ...
8
votes
4answers
369 views
How can I automate this tensor computation?
I am doing this work by hand, but it takes a lot of time and I make several calculation errors, so I was thinking to make Mathematica to calculate this for me, but I am stuck at the very beginning.
I ...
3
votes
2answers
57 views
Simplify the cubic root of cube assuming real and positive variable
I know this is very simple but I couldn't find a reasonable solution for it in the archive. It seems that my Mathematica does not take into account the assumptions when it wants to simplify the ...
0
votes
1answer
91 views
Why are some of my assumptions ignored?
In my opinion Mathematica should be able to further calculate and simplify the output of G1[...].
...
0
votes
0answers
37 views
Complex number manipulation
I want to simplify a complex expression like y * x * Conjugate[x] where y is a real number. Now mathematica is giving output as y x conjugate[x]. how can I get the answer as y abs[x]^2. "FullSimplify" ...
2
votes
1answer
76 views
Combining ArcTan's like in Maple
It seems to me there is no simple way to combine ArcTan's with complex arguments symbolically in Mathematica as it is in Maple (https://www.maplesoft.com/support/help/Maple/view.aspx?path=combine%...
1
vote
0answers
51 views
How to get results in terms of vector operations?
Is there a simple way to simplify an expression in terms of vector operations?
For example, when I evaluate this;
...
1
vote
1answer
104 views
How can I simplify a super long expression? [closed]
I am a brand new to using Mathematica, and currently using it for my thesis.
Essentially I have a really long expression made up of lots of parameters.
I am trying to reduce the size of the ...
0
votes
1answer
56 views
Factoring Algebraic Expressions [closed]
Say I have an expression
$$x = L-(L-N)y^2(1+AB)$$
is there a way I can use mathematica to put the expression into the form
$$x = M(1+\sigma B)$$
where $M$ and $\sigma$ are lumped terms?
0
votes
0answers
29 views
Sum over powers of roots of unity gives only partial answer
Mathematica seems to be unable to handle sums over roots of unity. For example, Simplify[Sum[Exp[2 Pi I a b/m], {a, m}], {b, m} \[Element] Integers] yields ...
1
vote
0answers
23 views
Inverse fuction of TensorExpand
Is there a way in mathematica to factorize/simplify a dot product? I.e. I have something like a.b + a.c (obviously more complicated expressions) and I would like to factorize terms like
...
0
votes
0answers
34 views
FullSimplify does not simplify at all
I have some problems simplifying things with FullSimplify. Suppose a matrix ...
3
votes
4answers
443 views
How can I simplify $\lim_{n\to \infty } \, \int_0^n e^{-x} \left(1-\frac{x}{n}\right)^n \, dx$?
How can I simplify $\lim_{n\to \infty } \, \int_0^n e^{-x} \left(1-\frac{x}{n}\right)^n \, dx$ ?
Limit[Integrate[(1 - x/n)^n/E^x,
{x, 0, n}], n -> Infinity]
...
