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

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6
votes
0answers
46 views

Strange behavior when setting NumericQ of a symbol

It happens both in v9&v10. If you try this a^0 a^0 (1/a)^(3/2) a^0 (1/a)^(5/2) Mathematica returns 1 (1/a)^(3/2) (1/a)^(5/2) It's trivial. ...
4
votes
1answer
44 views

Problem with Simplify, Sqrt, and Set: What's going on?

I am having some trouble getting Mathematica to simplify an expression of the form Sqrt[x]*Sqrt[1/x], where x>0. The problem is that x is assigned to some complicated form by the time Mathematica ...
1
vote
1answer
75 views

Force Mathematica to return numerical answer to (relatively) complicated differential function

I am trying to take the Laplacian of the LogDet of a 2x2 matrix that I call V\[ConjugateTranspose].V, and actually get a number out at the end. Why does Mathematica ...
5
votes
5answers
106 views

Isolating cross terms

I have a set of expressions that contains terms like $\frac{1}{(x + a + b)(c+d)}$. I would like to simplify the denominator so that products of $a,b,c,d$ are dropped, but $x c$ and $x d$ are kept. ...
0
votes
0answers
32 views

Automatically simplify all output in notebook

Is it possible to tell Mathematica to automatically simplify all calculations you ask it to perform in a certain notebook? You can type Simplify[...] or FullSimplify[...] for each command ... ...
0
votes
0answers
40 views

Why does Mathematica not restrict the domains of Rational Expressions?

As taught in High School Mathematics: $$\begin{array}{ccl} \left\{ {(x-3)(x+3)\over 5(x+3)} : \ x\ne -3 \right\} & \ne & \left\{ {x-3\over 5} : \ x\in\mathbb{R} \right\} \\ \left\{ ...
1
vote
0answers
70 views

FullSimplify missing trivial rewrite

I'm trying to understand why Mathematica fails to find the Stirling numbers in the second sum below: ...
1
vote
2answers
44 views

How to Simplify exponents?

I need to divide a Gaussian Mixture by it's widest component. When I do this, the exponents of the output end up a mess of terms in need of simplification, but ...
1
vote
0answers
74 views

Simplifying $e^x>1$, is this a bug?

Simplify[Exp[x] > 1, x ∈ Reals] results in no simplification, although Reduce[Exp[x] > 1, x, Reals] correctly ...
5
votes
2answers
210 views

Evaluating complicated trig without resorting to numerical methods

I have an angle theta given by Kx = (2/Sqrt[3]) ArcSin[Sqrt[3/10]]; Ky = (2/3) (ArcCos[(1/5) Sqrt[7/10]] - Pi); theta = Cos[ArcTan[Kx, Ky]]; This evaluates, by ...
0
votes
0answers
44 views

How to simplify cases given with Piecewise function?

MMA gives me an answer in the form $$ \begin{cases} f(k_1) & k_1=k\\ 0 & else \end{cases} $$ which is obviously just $f(k)$. Can I make MMA simplify this expression to $f(k)$? The ...
2
votes
3answers
73 views

Drop terms in expression

Suppose I have an expression of the this type: Quantity["Epsilonzero"] a (b + c Sin[ω t])^2 where t is time. I am interested in "extracting" the non ...
0
votes
0answers
9 views

Simplifying faculties to reasonable numbers to figure out the median [migrated]

i'm currently trying to figure out how i can reduce the size of the numbers below, in such case that i can reason with them. E.g. in this example i would like to figure out the median. A) 1000! B) ...
2
votes
1answer
67 views

What am I missing!? Simple symbolic sum not simplifying

I'm VERY confused: in what universe is the following not zero? FullSimplify[2*Sum[Subscript[f, i], {i, 1, q}] - Sum[2*Subscript[f, i], {i, 1, q}]] Mathematica ...
0
votes
0answers
75 views

Simplifying terms in a Sum expression

I have a sum in the form of pure function s = Sum[f[k], {k, 0, # - 1}] & of perhaps complicated terms f[k]. The terms ...
1
vote
1answer
65 views

How can I simplify the result of a differential equation by using my own defined expressions? [duplicate]

I want to solve the following differential equation with mathematica: α β * w''''''[ξ] + ( 1 + α - p ) * w''''[ξ] + p/β * w''[ξ] = 0 The answer seems at ...
0
votes
1answer
50 views

Simplifying an answer returned by DSolveValue

Consider the IVP: $$x'=\frac92-\frac{x}{300+2t},\quad x(0)=0$$ Working the solution by hand, the answer is: $$x(t)=450+3t-\frac{4500\sqrt3}{\sqrt{300+2t}}$$ Entering code and then attempting to ...
0
votes
1answer
50 views

PowerFactorial and Factorial

After some computation, I have obtained a function PowerFactorial[1, n, -1]. Clearly, PowerFactorial[1, n, -1] equals ...
0
votes
1answer
55 views

Simplifying square root expressions

I have read lots of questions on square root simplification on MMA, but I haven't really seen my problem posted (or understood a clear way to deal with this issue). I am simplifying some expressions ...
0
votes
1answer
73 views

Series expand root of quartic polynomial containing many real parameters and FullSimplify return `Indeterminate`

Using Mathematica I can get the Eigenvalues of the following matrix (using Quartics->True): ...
4
votes
1answer
57 views

TensorReduce not simplifying transpose for symmetric matrix?

I know Mathematica is not very good with symbolic manipulation of matrix expressions, but I was surprised to find that it can't reduce the following expression: ...
2
votes
1answer
64 views

Simplifying conditional expressions using assumptions does not work

I have a conditional expression f[x_] := x /; x ∈ Reals This works fine for normal numbers and symbols, e.g. ...
8
votes
1answer
245 views

How to simplify -a*z+a*z to 0 where “a” is an expression

Consider the following: a = 1+(x+y+z+u)^10000 (* Out[57]= 1+(u+x+y+z)^10000 *) e = -a*z+a*z (* Out[59]= z (-1-(u+x+y+z)^10000)+z (1+(u+x+y+z)^10000) *) How can ...
0
votes
3answers
82 views

How can I write a do loop as a table?

I have a do loop that looks like this: Do[a = -1; b = 1; c = n; d = a + b + c; Print[d], {n, 1, 12}] which gives the output: 1 2 3 4 5 ...
4
votes
2answers
362 views

Force a negative square root to be interpreted as an I

I have expressions like $$\sqrt{-\sqrt{1+x^2}} $$ how can I force mathematica to systematically rewrite this as $$i(1+x^2)^{1/4} \quad ? $$
1
vote
2answers
52 views

Simplify power of KroneckerDelta

Why doesn't Mathematica simplify the following expression: FullSimplify[KroneckerDelta[x,y]^3] Since KroneckerDelta only ...
0
votes
0answers
52 views

Computation doesn't Finish

I'm trying to solve some problem by the following code: ...
3
votes
2answers
124 views

Replace expression, but only “outside” of a function [duplicate]

I have a horrid expression, which is basically a sum of exponents with coefficients. Here's a taste: What I want to do is to replace ks with another expression, ...
8
votes
0answers
99 views

Why is this evaluation halved when adding units?

Why does this strange behavior occur when dealing with units and quantities? ...
3
votes
1answer
65 views

Merge Roots of Polynomial

How can I make mathematica "merge" solutions of a polynomial by using $\pm$ instead of listing the two solutions fully with only one sign difference? In particular, I am looking to "compactify" the ...
0
votes
0answers
71 views

Symbolic Tensor Algebra

I need to perform basic tensor algebra in order to double check some very complicated simplification. It's nothing fancy, it just has so many factors by the end that it's hard to tell if an error has ...
2
votes
2answers
81 views

Let mathematica combine integral limits

Is there a way to teach mathematica to combine integral limits according to $\int_a^b f dx+\int_b^c f dx=\int_a^cf dx$ to simplify expressions like $\int_0^1 f[t] dt+\int_1^x (1+f[t]) dt$ to $\int_0^t ...
5
votes
2answers
157 views

How to simplify Boolean expression

I would like to simplify $$((p\oplus q)=True)\wedge(p=True)$$ to $$q=False$$ I was hoping BooleanMinimize[((p ⊻ q) == 1) ∧ (p == True)] would do the trick, but ...
2
votes
0answers
63 views

Extract common factor from vector or matrix

I can't believe this hasn't been asked before but I can't find anything. Is there a way to convince Simplify or FullSimplify to ...
3
votes
0answers
97 views

Why does Mathematica show 4095/4096 terms in TrigExpand?

Clear[x, n]; expr = Cos[x]^(n - 2) (1 - Cos[x]^2 + Sin[x]); r=TrigExpand[expr] Where do those 4095/4096 comes from? It is correct, but it seems very strange ...
0
votes
0answers
70 views

Trying to Simplify an Expression

I'm trying to simplify an expression: ...
3
votes
4answers
153 views

Simplify binary expressions

Is it possible for Mathematica to do simplifications for expressions where the variables are binary, such as: a + b = 1 + 2*c => a + b = 1 Here c must be 0 because if it is 1, the RHS is 3 but ...
6
votes
1answer
136 views

How to prevent simplification?

I have a question about the concept of simplification. I want to explain it with an example. When I write $4/8$ in mathematica, output is 1/2. How can i return ...
1
vote
1answer
33 views

hold specific pattern in symbolic calculation

I encounter some questions when I try to simplify a symbolic expression using Mathematica. For example, I got an intermediate expression ...
2
votes
1answer
50 views

Prevent Simplify from using cot

I have the following problem. I got a huge equation to simplify and in there are numerous $\cos(x)$ and $\sin(x)$ terms and now it happens that Simplify changes terms like $(...+\cos(x)*a+...)$ to ...
3
votes
1answer
118 views

Write Integer powers as products

I need to wirte all occasions of (a+b)^3,Ftp^2, Sin[th]^2, ...etc as (a+b)*(a+b)*(a+b), Ftp*Ftp, Sin[th]*Sin[th], ...etc ...
0
votes
0answers
38 views

Using assumptions when calling Simplify from Collect

I am quite new to Mathematica, so please be patient ;) I have a very long equation that I have to sort for powers of a variable called e and that I want to ...
6
votes
4answers
140 views

Minimizing a function with a constant $l > 0$

I'm VERY new to Mathematica and would like some help with minimizing a function. $$f(x) = \frac{1}{2} \sqrt{\frac{\left(l^4+x^4\right)^2}{l^4 x^2}}$$ I want to find which $x-value$ (probably ...
2
votes
1answer
87 views

FullSimplify wont simplify to expression with lower SimplifyCount

I have been trying without success to get FullSimplify to work on some trigonometric expressions. It refuses to convert them to forms that are clearly much ...
3
votes
2answers
214 views

Fullsimplify does not simplify Abs'[1.-a]

I have to simplyfy an expression involving Abs' This works: FullSimplify[Abs'[1 - a], a ∈ Reals] Sign[1 - a] but this ...
4
votes
3answers
372 views

How to transform power of -1 into exponential [duplicate]

After FullSimplify, Mathematica usally gives some coefficients like ((-1)^(1/5)) But I don't want this form, I want ...
1
vote
1answer
48 views

simplification issues

The first are from an old paper, dealing with the evaluation of elastic Green function in a transversely isotropic medium (Hill 1964). ...
1
vote
0answers
72 views

Apart for complex roots?

Let p[x] be a polynomial in x and consider the partial fraction decomposition of 1/p[x]. ...