Questions on manipulating complicated expressions and making them look simpler using Simplify, FullSimplify and Reduce.
4
votes
1answer
144 views
6
votes
4answers
2k views
Factoring polynomials to factors involving complex coefficients
I've run into some problems using Factor on polynomials with complex coefficient factors. Reading the documentation it looks like it only factors over the ...
2
votes
3answers
57 views
Problem with simplifying Sinc function
$Assumptions = x ∈ Reals && y ∈ Reals && a ∈ Reals && b ∈ Reals;
These work:
...
1
vote
0answers
16 views
Rationalizing Denominators with Radicals [migrated]
How do you rationalize this fraction:
1/(sqrt(n+1))
2
votes
2answers
43 views
Expanding Matrix Expressions
I want Mathematica to recognize that
A.(-B.C)+A.B.C = 0
Yet FullSimplify and the like leaves the expression as it is. How do I get around this?
4
votes
2answers
220 views
Simplify — is this simplest result Mathematica can provide?
I have a question about Simplify: When I do a simplification the returned result is not as simple as I want. When I ask for the Norm of an complex expression, ...
2
votes
2answers
93 views
Substitution to write out powers of expressions
I am looking for a substitution command which will write out powers of expressions like this:
$$\frac{a ~b^3~ c}{d~ e^{3/2}~ f^2}\to \frac{a ~b~b~b~ c}{d~ e^{1/2}~ e^{1/2}~ e^{1/2}~ f~f}$$
...
13
votes
3answers
176 views
Common subexpression from two expressions
I am working with some unpleasantly tedious polynomials, which need to be manipulated in various ways (integrate with respect to some variable, differentiate with respect to another). Since these ...
4
votes
2answers
129 views
on simplifying an expression
After some integration process, I ended up with the following expression:
...
2
votes
3answers
133 views
Join all square root expressions?
Sometimes I observe Mathematica produce expressions exactly like the following after a simplification step:
$$\frac{a+\sqrt{-(1-b)}\sqrt{\frac{1}{b-1}}}{\sqrt{c}\sqrt{\frac{1}{c}}}$$
Now, any ...
1
vote
1answer
100 views
Improve performance for finding Fibonacci number which have divisibility property
In this post, the OP requires finding a Fibonacci number having some divisibility property with Mathematica and Maxima. I tired tried that Mathematica code on Mathematica 9.0 and it's still slow ...
12
votes
1answer
95 views
How to instruct FullSimplify to assume that PossibleZeroQ returns correct result?
Sometimes I have a really huge expression that cannot be significantly simplified by FullSimplify. I would like to, so to speak, "simplify with faith" using ...
1
vote
1answer
100 views
Assumptions are not being applied to integral
I am trying to use assumptions to simplify an integral, but I can't seem to get the assumptions to apply themselves. Here is the code I am using:
Note the expressions in the assumption can be found ...
0
votes
1answer
85 views
Simplifying Complex Numbers that contain physical units
I am trying to evaluate the following:
Simplify[Meter Nano Re[(a + I b)/(Meter Nano)], Assumptions -> Element[{a, b}, Reals]]
However, Mathematica returns:
...
2
votes
0answers
54 views
Simplify yelds an incorrect expression [closed]
I was trying to simplify an expression:
DSolve[d'@t == a + b Sin@d@t, d@t, t]
Simplify[%, Abs@a < -b < 0]
and I got
...
0
votes
2answers
50 views
Conjugate and simplify
I want to get a cosine from taking the real part of a complex exponential: $cos(x) = Re(exp(i x))$. What I do in Mathematica is
...
3
votes
3answers
144 views
Mathematica not able to confirm its own solution to differential equation
I type the following into Mathematica:
DSolve[q''[x] + 2 x/(x^2 - 1) q'[x] - 4*q[x]/(x^2 - 1) == 0, q[x], x]
It gives me the result
...
3
votes
2answers
202 views
Mathematica does not understand (R^3)^(1/3) is the same as R [closed]
In the output from a calculation in mathematica stands a/((R^3*c)^(1/3)), with c and a ...
2
votes
2answers
145 views
How to expand a general expression in cross and dot product in Mathematica
I am looking for a way to simply the general expression in cross product and dot product with general vectors. I got a help in How do I simplify a vector expression? but soon I find that it doesn't ...
4
votes
2answers
175 views
Is there a way to show the details of a numerical computation?
I have recently started using Mathematica as a calculator while teaching (definitely overkill, but I try to use as few tools as possible). I would like my students to be able to trace simple numerical ...
0
votes
0answers
49 views
Any way to fully expand an expression of two operators?
I am looking for a way to expand a complicate expression like the follow
(A o B + C o (DxE))*(D o (ExF) - ExA + A)
Here o and x are the operator. I want to ...
1
vote
1answer
75 views
Set all instances of Exp[-x_] to zero?
To simplify a huge expression efficiently, which involves a variable in a bunch of exponential functions going to infinity, I have tried to substitute
...
1
vote
1answer
83 views
Trying to show an expression is always zero
I have a symbolic matrix
$$m = \begin{pmatrix}A1 & B1 & C1\\A2 & B2 & C2 \\ A3 & B3 & C3\end{pmatrix}$$
and I believe that Det[m] is ...
0
votes
1answer
61 views
Avoid trigonometric simplifications?
When evaluating the expression
Sinh[x]^2 + Cosh[x]^2 // FullSimplify
I get
Cosh[2 x]
That is indeed a simplification, but ...
1
vote
1answer
48 views
Simplify expression to Abs
FullSimplify[Sqrt[1/(a^2 b^2)], Element[{a, b}, Reals]]
gives
Abs[1/(a b)]
How do I simplify the following expression
...
9
votes
1answer
287 views
Simplify Sin[x]/x to Sinc[x]
I have an expression in the form of $\tt \frac{Sin[x]}{x}$ that I would like to simplify to the form of Sinc[x]. I've tried the ...
5
votes
1answer
75 views
How to apply tags to expression terms?
I often see on this site and at the mathgroup the repeated questions on how to rearrange expression that Mathematica "likes" to keep in one form, but the user prefers in another. Consider this trivial ...
4
votes
1answer
97 views
Simplifying numerical expressions involving special functions
I've encountered the following problem. There is the identity that the special functions EllipticK[x] and EllipticE[x] satisfy:
...
1
vote
0answers
60 views
Problem with using Assumptions in Simplify [closed]
I want to simplify
Log[E^(2 \[Pi] I m/n)]/(2 \[Pi] I)
To obtain m/n.
I have tried
...
4
votes
2answers
166 views
Simplify expressions with Log
How can I get Mathematica to simplify the following expression
n Log[a] + m Log[b] - m Log[a + b] - n Log[a + b]
into
...
0
votes
0answers
108 views
6x6 matrix NullSpace
I'm working with a 6x6 matrix. Whenever I try to find the NullSpace and FullSimplify it, I get the error
No more memory ...
9
votes
4answers
157 views
FullSimplify Over Reals Automatically
Frequently, Mathematica will produce some expression in a complicated form, with a number of unset variables. For me, it is rare that I would be interested in solutions that are generalized to both ...
5
votes
2answers
244 views
Log of products to sum of logs
I have a log of products:
$$\log \left(\prod _{i=1}^n \left( g(a(i,i)) \prod _{k=1}^i f(a(i,k))\right)\right)$$
That I turn into a sum of logs (I know everything involved is nice enough):
$$\sum ...
2
votes
2answers
90 views
Puzzling behavior produced by Exists
I need to simplify a set of solutions of a system, say for example:
...
0
votes
1answer
78 views
Simplify expressions that contain full derivatives
The best way to show what I want is by giving an example:
How to go from
...
-2
votes
2answers
204 views
How to simplify expressions containing derivatives
Is there a way to reverse the application of derivative rules in order to simplify expressions including derivatives?
e.g. in
Mathematica code:
Want to go from
...
0
votes
2answers
146 views
Simplifying a trigonometric equation to obtain specific terms
When I try to solve the non-homogeneous differential equation
...
0
votes
0answers
68 views
Choosing the appropriate solution for the square root [closed]
My problem is the following: given the function
myfunc[x_, a_]:= (a^3 - (a^2)^(3/2))/(x)
the limit as x goes to 0 should be well defined and = 0. However,
...
1
vote
1answer
49 views
Declaring a positive variable [duplicate]
Why I have this behaviour?
R /: Greater[R, 0] = True
R > 0
=> True
Simplify[Sqrt[R^2]]
=> Sqrt[R^2]
I expect R ...
6
votes
2answers
295 views
How do I simplify a vector expression?
I am doing vector analysis. I have figured out that the following expression won't be simplified in Mathematica:
Simplify[Dot[x, y] - Dot[y, x]]
I think the ...
7
votes
2answers
362 views
Simplifying the derivative of $|x|$
Context
In[855]:= D[Abs[x], x] /. x -> 1
Out[855]= Derivative[1][Abs][1]
In[856]:= D[x, x] /. x -> 1
Out[856]= 1
Question
Why is ...
2
votes
1answer
138 views
Variable substitution in sum's index
How cam I simplify
Sum[UnitStep[-1 + n]/Sqrt[n!], {n, 0, ∞}]
to
$$\sum _{n=1}^{\infty } \frac{1}{\sqrt{n!}}$$
and then to
$$\sum _{n=0}^{\infty } ...
1
vote
2answers
99 views
Construct a sum that evaluates its arguments but doesn't evaluate further
I'm trying to construct a sum like this:
Sum[body, range]
where body is
...
3
votes
2answers
153 views
Combining and separating sums
How can I combine or separate sums in Mathematica in the way that Together or Expand work for rational expressions？
For ...
1
vote
3answers
77 views
Auto simplifications of power products
Mathematica automatically simplifies Exp[a]Exp[b] to Exp[a+b]. The problem is now that I can't do this ...
11
votes
0answers
515 views
Simplify matrix algebra
I'm trying to simplify some matrix linear algebra, for example, simplify
$$\big(a1\times(A1\cdot A2)\big)\cdot\Big(a2\times A3\cdot A4+(a3\times A5)\cdot(a4\times A6)\Big)^{T}$$
where lower case ...
0
votes
1answer
80 views
Mathematica not simplifing when using FullSimplify
I am trying to simplify the following $(Z_i - Z_{i+1})^4$ using
...
4
votes
1answer
160 views
Properly Force Mathematica to Simplify Log Expressions/Rules
I want to be able to expand $\log(x^n e^x) = n \log(x) +x$:
FullSimplify[Log[x^n Exp[x]], x > 0 && Element[n, Integers] && n > 1]
yields
...
5
votes
1answer
158 views
Is there a way to track the Simplify process?
Is there any way to track how Mathematica actually performs Simplify, so that we can see what those "Automatic" transformation functions it applies are and how it ...
0
votes
0answers
106 views
How Simplify and Assume can be combined on matrix products?
What I am trying to do is to simplify some expressions involving matrices! The problem is that Simplify[] considers the simplifications based on alphabetical order and everything is Commutative. For ...
