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

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2
votes
3answers
115 views

How to delete a pattern from String?

Having a string like : "{Aaaa -> a, Bbbb- > b, Cccc -> , Ddddd -> c, Eeeee -> , Fffff -> e}" I want to delete the parts that contain ...
0
votes
1answer
73 views

Strange evaluation of an sum involving binomial coefficients

I stumbled upon this problem while playing with Mathematica 10. Can anyone help me explain the following behaviour? I define a sum ...
0
votes
0answers
27 views

How to simplify this expression without this particular substitution?

I have the expression expr = -(m-2 r+b^2 (-7 m+6 r)) ((-m+r)^2+b^4 (-2 m+3 r)^2+b^2 (-3 m^2+10 m r-6 r^2))+(1+b^2)^2 m^3 Cos[t]^2 , to which I can bring to this ...
1
vote
3answers
141 views

Simplify a composition of functions

How do I make Mathematica simplify, for example, (1-#&)@*(1-#&) into #&? ...
0
votes
1answer
42 views

How to manipulate string parts?

Let's consider I have following string: "{a-> POR, b-> D610, c-> 0, d-> \"300/7\", e -> \"1/400\"}" How can I run over and update anything that is ...
2
votes
1answer
80 views

How to parse string to expression? [closed]

When trying to make a string an expression I see some wrong results: ...
0
votes
1answer
95 views

Simplified expression is different than original

I have a question regarding the Simplify command in mathematica. I am working with a 4 x 4 table called Eqs, filled with symbolic expressions. I then do ...
2
votes
1answer
238 views

Another square-root simplification problem

In a certain sequence of computations, sometimes I'll get an expression of a form such as Sqrt[u^4 + 4 u^6] which it is necessary to have converted ...
0
votes
0answers
45 views

How do I simplify Interval[{x,x}] to x?

How do I simplify Interval[{x,x}] to x ? Simplify and FullSimplify do not seem to do it.
1
vote
1answer
63 views

Applying functions repeatedly on parts of complicated expressions

I am dealing with expressions like $$ \textrm{expr}=5D_{4,1}\langle12\rangle\langle23\rangle\big(-\langle15\rangle^2\langle24\rangle\langle34\rangle + ...
2
votes
0answers
66 views

Simplify large fractions

Hi i'm quite new with Mathematica and i'm experiencing some problems with Simplify and FullSimplify. I'm dealing with a sistem ...
0
votes
0answers
15 views

Collecting and simplifying polynomials [duplicate]

I want simplify some expressions but also using an ordered form for a polynomial. Collect[..., Q, Simplify] should do the job, but sometimes the results does not ...
0
votes
0answers
79 views

Simplifying trig function

I'm trying to simplify a long expression of trig function. I'm not particularly good at trig identities or Mathematica, so this is turning out to be quite a task :( I tried Simplify, FullSimplify, ...
1
vote
0answers
33 views

Simplifying And of equality expressions

This expression does not automatically simplify to False: a == 0 && a != 0 ...
1
vote
1answer
58 views

Simplifying a product with indices by implementing a rule

I want to simplify a product of two operators including indices. Let's say my operators are $$ \mathcal{O}^{\mu \nu, \alpha \beta} = -p^2 \left( \eta^{\mu \alpha}\eta^{\nu \beta} + \eta^{\mu \beta} ...
1
vote
1answer
33 views

How to simplify D[(1/2).m.(X[t]^2), {X[t]}] [closed]

I would like to simplify the following expression: D[(1/2).m.(X[t]^2), {X[t]}]// Rationalize // FullSimplify // TraditionalForm This should evaluates to: ...
1
vote
1answer
80 views

Simplifying complicated fractions

I need to simplify a long expression with a denominator in the form of a+b. To keep it simple, let me replace the long expression with a short example: ...
0
votes
1answer
65 views

Is it possible to reach this expression using Mathematica's algebraic functions?

I know that this expression: -(m-2 r+b^2 (-7 m+6 r)) ((-m+r)^2+b^4 (-2 m+3 r)^2+b^2 (-3 m^2+10 m r-6 r^2))+(1+b^2)^2 m^3 Cos[t]^2 Is equal to this one: ...
1
vote
1answer
44 views

Simplify CubeRoot of meter cubes

Why Mathematica doesn't simplify CubeRoot of meter cubes to meters? r = Quantity[10, "Meters"]; v = 4/3 r^3 Pi; CubeRoot[% * 3/4 / Pi] returns ...
1
vote
2answers
61 views

Abs[Sin[4a]] not equal to 2Sin[2a]Abs[Cos[2a]] for a in [0,\pi/2]

I have a long expression which is not fully simplified because Abs[Sin[4a]] is considered different from 2Sin[2a]Abs[Cos[2a]] ...
4
votes
1answer
49 views

Simplify complex answer given by DSolve[]

I tried the technique in this question, but that did not work for the solution given by the MWE: DSolve[{f'[t] + f[t]*g[t] == h[t], f[0] == f0}, {f[t]}, t] How ...
2
votes
1answer
89 views

simplifying integrals for multiple exponentials

This is somewhat related to this question, but applied to products of Exp[]. For example, I have a symbolic expression containing terms like $Exp[\int_0^1 ...
1
vote
1answer
85 views

Is there an easy way to let mathematica print out every Erfc and InverseErfc as F and F^{-1}

Mathematica uses complementary error function and its inverse as functions for example when integral of a Gaussian is taken. Therefore, all output expressions of Mathematica involve Erfc and ...
2
votes
1answer
157 views

Is there a way to simplify a symbolic expression at assignment, once-for-all?

I have a series of symbolic function calls that could be greatly simplified using some assumptions. I think I would like for these assumptions to be used in the definition of the function so that they ...
2
votes
1answer
58 views

Pull out scaling factor from a denominator

How do I force mathematica to just pull out the scaling factor of 1/r from this expression. (a+b)/r edit: Sorry, perhaps my earlier formulation of the question wasn't clear enough. I would like ...
0
votes
0answers
28 views

Extract the divergent/bounded part of a certain expression

Consider I have a power series which is function of $x$. A part of this expression is bounded when $x->\infty$, some remainder is on the other hand divergent when $x$ goes to infinity. What is the ...
0
votes
1answer
47 views

Series identity with binomial coefficients [duplicate]

I have this apparently simple equation: ...
2
votes
1answer
58 views

Arrange equation in normal form

Is there a way, or if not, how could one define a function which takes an equation in any form (for example as given by FullSimplify): $$(A+X_0) x+By=3x$$ and ...
6
votes
1answer
92 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
71 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 ...
2
votes
1answer
111 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
127 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
50 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
77 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
107 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 ...
5
votes
2answers
243 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
60 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
80 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 ...
2
votes
1answer
74 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
93 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
71 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
56 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
60 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
124 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
84 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
73 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
83 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. ...
9
votes
1answer
251 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
89 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
385 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 $$i(1+x^2)^{1/4} \quad ? $$