I am having some trouble with this problem: Let $\omega$ be a complex number such that $\omega^5 = 1$ and $\omega \neq 1$. Find $\frac{\omega}{1 + \omega^2} + \frac{\omega^2}{1 + \omega^4} + \frac{\omega^3}{1 + \omega} + \frac{\omega^4}{1 + \omega^3}$, (precalculus, roots of unity). Does anyone have any hints? I tried rearranging it to cancel some terms out in the fractions but it ended up becoming a large, messy fraction.
not that I've tried working anything out on paper but it might get nicer if you multiplied the first term by $\frac{\omega^4}{\omega^4}$, the second by $\frac{\omega^3}{\omega^3}$, etc.
okay I worked it out and it simplifies really nicely
Where are you taking pre-calc? At least where I'm from, we hardly touched complex numbers, much less roots of unity, but then again, I didn't exactly have a stellar math education.
It wasn't used in solving this particular problem, but as a side-note, in future problems it might be useful to remember $1+\omega+\omega^2+\omega^3+\omega^4=0$, so the final fraction (although it simplified without realizing it) could have been seen as $\frac{-1}{-1}2$
I'm working as a grader for a linear algebra course this semester, and have found that they were taught the definition of a determinant of a matrix as $det(A)=\sum\limits_{P\in \text{patterns}(A)} sgn(P)prod(P)$. I'm curious if anyone else here learned this definition before the recursive definition.
I can tune by ear to most things, but that's the ten or so years of piano at work, giving me a damn decent sense of pitch (I tend to be only a few cents flat).
(How do you post videos like that? Just put the link in?)
I don't really listen to much metal--I don't know why, just something about it turns me off--but there's no denying that it takes an immense level of technical skill to do it well.
They were quite technically skilled, but didn't concern themselves with typical notions of consonance and dissonance--they cared more about the "wall of sound", so to speak, the texture and timbre of the guitars as they weave between one another.
so I was on the radio yesterday for a quiz, and the RJ asked me what genres of music I liked. I said "upto 19th century classical, inclusive, some metal and jazz, and . . . dramatic pause Pink Floyd".
@Khallil I believe it was done with $\LaTeX$, by offsetting the longrightarrow $\longrightarrow$ some amount to the left. That is, Soham put it there (to emphasize that in fact, he is the fan) :)
Most things before that I have. But I'm seeing everything presented differently from when I was introduced to it, and his writing is so lucid. It's great.
I agree that you should get exercises elsewhere since his are rather tepid, but I agree with your taste in the book. I think I said this earlier but it's where I learned my algebra.
That was a valid counterexample from before @SohamChowdhury. Both of those quotient groups have order $2$, so there's only one thing they could be. And obviously $C_4 \ncong V_4$.
Python does support functional-ish ideas, so it's a good gateway drug.
Say you have some list of numbers $l$ and a function $f:\Bbb R^2\to\Bbb R$ defined by $x\mapsto 2x$. You can get a list $l_2 = \rm{map}(f,l)$, which does exactly what you think it does: it doubles everything.
@SohamChowdhury: No, they don't. It's just terminology overload. Free as in 'does not fix anything', which one might say as 'nothing is restricted', or 'free'.
Can someone point me to a reference to the fact any two semisimple categories are equivalent if and only if the numbers of their isomorphism classes of simple objects are the same?
off topic. Suppose $N$ is a normal subgroup of $G$. I know that $(gn)N=gN$, but I'm not sure whether $(ngN)=gN$. Is the latter always true? It's not obvious to me since $ng$ need not be in $N$.
In mathematics, the n-sphere is the generalization of the ordinary sphere to spaces of arbitrary dimension. For any natural number n, an n-sphere of radius r is defined as the set of points in (n + 1)-dimensional Euclidean space which are at distance r from a central point, where the radius r may be any positive real number. Thus, the n-sphere centred at the origin is defined by:
It is an n-dimensional manifold in Euclidean (n + 1)-space.
In particular:
a 0-sphere is the pair of points at the ends of a (one-dimensional) line segment,
a 1-sphere is the circle, which is the one-dimensional c...
@skillpatrol oooooooo, "In the study, mathematicians rated Srinivasa Ramanujan's infinite series and Riemann's functional equation as the ugliest of the formulae." :-(
"Brain scans show a complex string of numbers and letters in mathematical formulae can evoke the same sense of beauty as artistic masterpieces and music from the greatest composers."
So in $\mathbb{R}^2$, the distance between $(x, y)$ and the origin is $\sqrt{x^2 + y^2}$. So all the $N$-sphere is is the collection of points in $\mathbb{R}^{n+1}$ that are all the same distance from a given point.
That's pretty much all there is to it. Now, it's true that the $N$-sphere is a manifold, and there are tons of equivalent ways of defining a manifold. One way of thinking about a manifold of dimension $n$ is that a small neighborhood around any given point is "homeomorphic" to $\mathbb{R}^n$.
A homeomorphism is a function from one space to another that is bijective, continuous, and has a continuous inverse.
Well, it's hard to explain what a manifold is just right off the bat.
Well, an $n$-dimensional manifold "looks like" $\mathbb{R}^n$ locally. So if the Earth was a perfect sphere, it would be a $2$-dimensional manifold because you can't really tell the difference between the ground you're standing on and a plane ( $\mathbb{R}^2$ ) @zed111
And likewise the $1$ sphere, what we call a circle, is a manifold because it "looks like" a straight line ( $\mathbb{R}$ ) if you're standing at a point and looking at points very close to you.
And there are ways of making these statements mathematically rigorous.
@skillpatrol The hugely influential theoretical physicist Paul Dirac said: "What makes the theory of relativity so acceptable to physicists in spite of its going against the principle of simplicity is its great mathematical beauty. This is a quality which cannot be defined, any more than beauty in art can be defined, but which people who study mathematics usually have no difficulty in appreciating."
@Soham another tautological corollary of group actions : let $G$ act on the underlying subset of $G$ by conjugation : $gx \mapsto gxg^{-1}$. partition $G$ into the orbits of this action. $|G| = \sum_i |O_i|$. for each elt in $Z(G)$, the orbit is of card. 1. for the other $|O_i|$s, apply orbit stabilizer to conclude $|O_i| = |G : C_G(x_i)|$ where $x_i$ is some representative of that class. now sum up.
the resulting thing is called the class equation of $G$.
@KarlKronenfeld :P
@Karl I guess I am just ignorant towards category theory (probably because I don't know much mathematics)
Sarcasm is "a sharp, bitter, or cutting expression or remark; a bitter gibe or taunt." Sarcasm may employ ambivalence, although sarcasm is not necessarily ironic. "The distinctive quality of sarcasm is present in the spoken word and manifested chiefly by vocal inflections". The sarcastic content of a statement will be dependent upon the context in which it appears.
== Origin of the term ==
The word comes from the Greek σαρκασμός (sarkasmos) which is taken from σαρκάζειν meaning "to tear flesh, bite the lip in rage, sneer".
It is first recorded in English in 1579, in an annotation to The Shepheardes...
woo. but I'm very excited about starting rings. because 1) I learn what homology is, properly; 1b) diagram chases; and, the most important of all: 2) number-theoretic applications like the Christmas theorem
@Chris'ssistheartist sorry ,, I keep forgetting about it .. I'll try it sometime later .. there are a bunch of trouble at hand I have to deal with first ..