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

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11
votes
1answer
119 views

What's wrong with Simplify and FullSimplify?

I have a quite complex list of equations and inequalities I combine to a boundary condition for my cost function. After investigation of two days I found the bug (I really name it a bug!). One of my ...
4
votes
1answer
73 views

What options need to be set for Simplify to perform a certain manipulations similar to FullSimplify?

Simplify performs algebraic transformations and is fast, while FullSimplify tries a wide range of transformations involving ...
0
votes
0answers
42 views

How to express $f(x,y) = u(x,y) + i\, v(x,y)$ as $f(z)$ [on hold]

The $f(x,y)$ is actually a series with complex parts. I'd prefer not working this out by hand.
0
votes
1answer
25 views

How can I manipulate a long expression to order it by factors/derivatives of a particular function?

I have a Mathematica notebook that generates a linear expression involving derivatives of a given variable. Expanded (and simplified for our purposes), it looks something like this: \begin{equation} ...
1
vote
0answers
41 views

Inverse Laplace computation Mathematica

I have a transfer function such as following, which I would like to find its inverse: F=(a*s^2)/(b*s^3+c*s^2+d*s+e) I have a numeric value for a b c d and e but ...
10
votes
1answer
138 views

Using Simplify on a consistent system returns False

Bug introduced in 8.0 and persisting through 10.1.0 or later It's late, but am I missing something here? Why should two independent equations, which together are consistent, ...
2
votes
1answer
88 views

Simplification of exponential

I would like to understand why FullSimplify doesn't entirely simplify this expression ...
0
votes
0answers
55 views

PolyLog does not simplify

How come mathematica can not simplify a simple expression involving the PolyLog function? An example is: You know that ...
1
vote
1answer
66 views

What am I missing on this part of the documentation?

In the documentation for FullSimplify, under Options > Assumptions it is stated that: When assumptions are given as an argument, $Assumptions is used as well: ...
2
votes
3answers
54 views

Simplifying Logs assuming arbitrary arguments real and positive

I have some expressions involving Logs which I would like to simplify. Unfortunately FullSimplify doesn't work because it assuming the arguments are general. I have no way of knowing a priori what the ...
0
votes
0answers
18 views

Not Simplify automatic some expression(values)

I try to calculate $$\text{res}\left(h(z) (\psi ^{(0)}(z)+\gamma )^2,\{z,-4\}\right)$$ the result is $$\frac{1}{6} \left(6 h'(-4)-25 h(-4)\right)$$ the result it is possible to write as $$2 \left(6 ...
0
votes
0answers
25 views

Create Linear System from derivatives of variables and solve it [duplicate]

I have the following simply function: f[x_, y_, z_] = (x - A)^2 + (y - B)^2 + (2*z - C)^2 + (5 + z + x - D)^2 + (y - 2 + 2*x)^2 + (y - z + F)^2 I am ...
4
votes
1answer
85 views

Collect without grouping terms

The built-in function Collect, when applied to more than one variable, will group expressions by the first variable, as here: ...
2
votes
1answer
64 views

Wrong result after Simplify of a complex variable with assumptions satisfying an inequality

Using Mathematica 10,Simplify[a\[Conjugate], Assumptions -> {(a + a\[Conjugate]) > 0}] returns a, i.e. treats ...
3
votes
0answers
50 views

simplify expressions into sum function

Is there a way to have Mathematica simplify long expressions involving sums of variables into expressions using a sum function? Suppose I have something like this: ...
2
votes
1answer
61 views

Failure in the use of FullSimplify

My question is about an apparent failure of the function "FullSimplify" to simplify an easy algebraic expression. This is the expression that I ask Mathematica to evaluate: ...
0
votes
0answers
17 views

PolynomialGCD in complex numbers for vector simplification

I wanted to define a function $f(t,\vec{r})=e^{i\omega t-i\vec{k}\cdot\vec{r}}$, and take gradient of it. With, ...
3
votes
1answer
97 views

How to control cancellations with Simplify functions?

FullSimplify only simplifies the result of the following calculation halfway, leaving a lot of $e^{x^2/v}$ and $e^{m^2/v}$ terms that could have been cancelled: ...
0
votes
0answers
44 views

Is there a function equivalent to rewrite function in Sympy

Sympy provide rewrite function to rewrite expression in terms of other functions. ...
1
vote
2answers
54 views

Common subexpression elemination of complicated function by nesting using HornerForm and Experimental`OptimizeExpression

I want to have common subexpression elimination of comlicated functions where the elimination is done by factoring out the expressions. The result is not to be digested by a compiler, it should remain ...
0
votes
2answers
89 views

Simplify large sum of fractions to shortest representation

I appear not to be able to find a way to simplify the sums of fractions like the following example to their shortest representation. For me shorteste representation means, to have as few as possible ...
0
votes
1answer
48 views

Equation simplification

Given that: ...
4
votes
3answers
76 views

Automatically split an expression and use TrigFactor to solve the parts

I want to simplify the following expression: 1/2*(Sqrt[3]*Cos[x]*la - Sin[x]*la - lb + Sqrt[3]*Cos[x+y]*lf - Sin[x+y]*lf) I used ...
5
votes
2answers
147 views

Trigonometric simplification

How can I simplify 1/2 (Sqrt[3] Cos[x] - Sin[x]) in order to get Cos[x + Pi/6] on Mathematica? I saw that Wolfram|Alpha lists ...
0
votes
0answers
47 views

FullSimplify cascades too much/groups variables too eagerly

This is something FullSimplify will give: $$\frac{n (s+\text{s2})-\text{a1} g}{\text{a1} (g-\text{a2} s)+s (s+\text{s1}) (s+\text{s2})}$$ I could find better examples where FullSimplify cascades ...
1
vote
0answers
39 views

Simplification with absolute value

I have a long expression that has absolute values in the exponent. Some parts of the expression would clearly simplify if one assumes that the power is an odd or even integer. When I give one of this ...
0
votes
1answer
67 views

How to shorten/simplify my plotting code

Is there a way to simplify and shorten my code? ...
24
votes
1answer
492 views

A better simplification function

I am creating this question and posting an answer to it as a help for those who have problems with Mathematica simplification oddities that appear in other questions on the site. First of all, there ...
2
votes
0answers
68 views

Factor out a constant from a matrix

I've got a matrix in which every entry is of the form x/4. I cant find out how to factor out the 1/4 so that the actual matrix is clearer. Thanks for your help!
0
votes
0answers
41 views

Evaluating an expression after making a rule

Just starting to use this language. I'm interested in making a rule, then evaluating the same rule. I can't get Mathematica to do what I expect/want, so I'd be interested in seeing what I should to to ...
1
vote
1answer
91 views

Solving a complex logarithmic equation

I am trying to solve the following equation for $x$, with integer $n$. (1 - ((-1 + x)^E x^(1 - x) Log[x]^-E)^(1/(-1 + E)))/(-1 + x) == n
5
votes
0answers
46 views

How to simplify expressions by closing open inequalities?

Recently I have often acquired results which consist of combinations of 0, 1 and 2-dimensional (in)equalities. For instance, consider a very simple case with ineq1 ...
2
votes
4answers
95 views

how to cancel arbitrary term in fractional formula

I often encounter this kind of problem that I want the fractional formula to be looked like the way I want it to be. For example, this one $$\frac{R^2 \left(g m_1-g m_2\right)}{J+m_1 R^2+m_2 R^2}$$ ...
2
votes
1answer
49 views

Dealing with functional equations

I have the specific function $G$ of $x$ satisfying the functional equation $G^3x=-1+G(1-x)+G^2x$. By using Mathematica, I would like to simplify the following polynomial of $G$ and $x$. $2 G^2 + 6 ...
9
votes
1answer
128 views

FullSimplify wrongly reduces expression to zero

I get the following output with a fresh Mathematica (ver 10.0.2.0 on Mac) session ...
1
vote
2answers
73 views

How to stop FullSimplify from returning Root objects

I have several expressions in a series, such as 1/4 (-(1/4) + Sqrt[5]/4 + I Sqrt[5/8 + Sqrt[5]/8]) (-1 - Sqrt[5] + 2 Sqrt[7/2 + (5 Sqrt[5])/2]) If I run ...
0
votes
2answers
68 views

How can I put the results of TrigFactor function into a more convenient form?

a1 D11 Cos[n x] + a0 a1 D11 Cos[n x] + 1/2 a1 a3 D11 Cos[n x] + 1/2 a2 a4 D11 Cos[n x] I have a large trigonometric expression. Can I factor out different ...
0
votes
0answers
40 views

How can I put the results of TrigReduce function into a more convenient form? [duplicate]

a1 D11 Cos[n x] + a0 a1 D11 Cos[n x] + 1/2 a1 a3 D11 Cos[n x] + 1/2 a2 a4 D11 Cos[n x] .......for example this expression can be written like ('expression') * ...
0
votes
0answers
44 views

Pulling out terms from an expression

I have an expression that is in a really complicated form but I know can be written like this: F[X,Y] = AX^2+BY^2+CXY where A,B, and C are complicated terms, but split up F[x,y] into a more ...
3
votes
2answers
99 views

How to simplify exponents of the form $\exp\left(i\frac{2\pi}{N}(N+1)\right)$ inside a function

I'm really annoyed with Mathematica and I need your help. I defined a discrete Fourier-Transformation(I use II instead of N, because Mathematica wont let me-.-): ...
2
votes
1answer
96 views

Inverse Laplace Transform difficulty

I am asked to find the inverse Laplace transform of: $$F(s)=\frac{2s^2+s+13}{(s-1)((s+1)^2+4)}$$ I did the partial fraction decomposition by hand and got: $$F(s)=\frac{2}{s-1}-\frac{3}{(s+1)^2+4}$$ ...
-1
votes
1answer
187 views

I don't want Erf[x]

I would much rather have the expression remain as an integral rather than have Mathematica convert it into $\mathrm{erf}$. Is this possible? I always end up differentiating the $\mathrm{erf}$ ...
0
votes
1answer
65 views

Simplify does not simplify

I have this expression Simplify[2 wb Z - 2 w xiR^4 Zb - 2 xiR^2 Sqrt[(wb Z - w xiR^4 Zb)^2/xiR^4]] which is actually zero when just calculated by hand, with ...
0
votes
2answers
75 views

Force Mathmatica to simplify an ArcTan[]?

I understand that there are many solutions that will produce the same arctangent, nevertheless I really need a simplification: ...
0
votes
1answer
47 views

Root: Simplifying symbolic expression

I'm doing calculations with a lot of symbols, which don't always gives nice expressions. Now I have a solution with a Root-expression, where the coefficients are symbolic, e.g. ...
0
votes
1answer
47 views
1
vote
0answers
85 views

Real part of a sum

I would like to take the real part of the following expression: Sum[(a[i] + I b[i]) r^i/(r^2 + z^2)^i, {i, 0, 2 n}] where all of ...
2
votes
0answers
47 views

Construct single InterpolatingFunction from a mathematical combination of other IF's

Let's say I have an interpolated function f, like I might get as the solution to an NDSolve: ...
1
vote
2answers
110 views

Collect distributed sums

I have another task that somehow should be trivial. Suppose I have the following expression $$ \sum_{i=1}^n \frac{2}{9} x_i + 2 \sum_{i=1}^n \frac{1}{9} x_i, $$ or in Mathematica-FullForm ...