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21:00
@BeginningMath What is D?
i'll check the name in english. just a moment
I know about permutations P and combinations C.
Maybe there are some other letters but not so standard in combinatorics.
But if you are just asking about P and C, I think Wikipedia will have lotsa info.
how can i transform $\binomial {10+k-1}{k}$ to a $\sum$ representation?
Oh, isn't that just given as a fraction? Why do you want a sum?
0
Q: Finish proof of tautology

N.ThompsonI'm new to Discrete math, I've been working on this problem for near an hour and can't figure out the next steps. The problem is: Show that [¬p ∧(p ∨ q)] → q is a tautology. Here is what I have so far. ≡ ¬[¬p ∧(p ∨ q)] ∨ q ≡ [p ∨ ¬(p ∨ q)] ∨ q ≡ [p ∨ (¬p ∨ ¬q)] ∨ q ≡ [(p ∨ ¬p) ∧ (p ∨ ¬q)] ∨ ...

21:04
just "binom"
not bionomial
resists temptation to submit automated proof as answer
because i'm asked to represent it in a sum
Mk, what type of sum?
0
A: Finish proof of tautology

Kenny LauAutomatic proof generated by Prover9: 1 -p & (p | q) -> q # label(non_clause) # label(goal). [goal]. 2 -p. [deny(1)]. 3 p | q. [deny(1)]. 4 q. [copy(3),unit_del(a,2)]. 5 -q. [deny(1)]. 6 $F. [copy(5),unit_del(a,4)].

fails
@BeginningMath Maybe if you post the whole question here, people can help you. But a sum is too vague.
21:08
how can you represent the equatition of putting 10 identical balls in k different basket in a $\sum$ sort of way?
In the context of combinatorial mathematics, stars and bars is a graphical aid for deriving certain combinatorial theorems. It was popularized by William Feller in his classic book on probability. It can be used to solve many simple counting problems, such as how many ways there are to put n indistinguishable balls into k distinguishable bins. == Statements of theorems == The stars and bars method is often introduced specifically to prove the following two theorems of elementary combinatorics. === Theorem one === For any pair of positive integers n and k, the number of k-tuples of posi...
As @Semiclassical and I discussed, I like to call this balls and walls instead of stars and bars, LOL.
in that way you get $\binom {9+k}{k}$. i need it in a $\sum$. this is what i don't know
+335 rep :O
@BeginningMath Hmm, and I don't know what kind of sum you are talking about, sorry.
@LeakyNun I hope when school starts you will be doing more work instead of earning reps, lol.
@Jasper lol
21:16
Seems like Irma is down to cat 2 now
that's much better
21:37
I finished a sandwich and you guys haven't said anything new.
@Dodsy How is school so far?
22:02
🏏 🏏
22:31
@Daminark What pic is that, lol
Cricket
LOL. Must be the sport and not the insect.
I was using it as a pun basically, like cricket cricket
22:53
@Daminark lol I didn't get it until you posted this
leaves room immediately upon seeing dastardly pun war
Why is Balarka even awake?
:P
Hi @Ted
23:10
shrugs
How's it going @Ted?
It's going. Had company here for the weekend and taught my first class this morning. So now I'm — as you guys like to say — chillin.
I was amazed today in my class by how many esoteric things one 9th grader had memorized.
What were they about?
And that's solid, had fun in class?
The one that amazed me was for knowing the 15-75-90 triangle (which I've never thought about before). But he could derive it using my favorite geometry theorem which most college students don't know (an angle bisector divides the opposite side ... — one of my standard first homework problems in the multivariable math class using vectors).
Wow, it's been ages since I've been here
wow, who the hell is Clarinetist?
(Am I going to get banned for bad language?)
23:18
LOL hi @Ted
rip in ban
So, what are you studying, Demonark?
He's procrastinating on K-theory
Some mix of k-theory/bundle stuff and number theory
Seems crazy to do K-theory before both algebra and topology.
23:29
He knows a nontrivial proportion of algebraic topology though
Atiyah's lectures build k-theory from the ground up, using only basic point-set and linear algebra
yeah, I guess so ... but what's the motivation?
@Balarka Ehh... Maybe overselling a bit, I know bits and pieces
Demonark: I gave that ninth grader one of my old favorite physics-y puzzles because he had finished all the exercises for the day.
Nice, which is it?
23:31
Two identical marbles are rolled with identical speeds across a table. One goes across flat. One goes through a dip in the table. Which one wins the race across?
And re motivation: right now my main motivation is that I know the tangent bundle is a thing that matters, and the stuff in general seems quite nifty
Can you use the k-theory you've learned to prove that the Hopf bundle is nontrivial?
Hello handsome folks
LOL, why, thanks, Kasmir.
Why is the operation ( -) not binary ?
@TedShifrin thought I change the way of greeting =p
23:34
What about us ugly people?
I've made little progress in k-theory, like I'm still learning the basics of operations on bundles :P
Operation on what set, Kasmir?
thats the thing ><
the book stated that in general
i think its a typ
its not birany on Natural numbers only
It's definitely not an operation on $\Bbb N$.
or maybe on some other subgroups where it wil fail to be closed
23:36
But it certainly is on a ring.
Or a general abelian group.
if you have the book by dummit and foot
page 16
the map a--> -a is not a binary operation
That's different, dammit.
It's a UNARY operation.
whats unary ?
It only acts on one (not two) elements.
damn it :D
I got it now
But why do they put it in such not clear way ><
23:38
It's totally clear.
A binary operation needs two inputs.
hmm if you read the context they put it
its not that easy to get if you are new on the subject
anyway thanks for clearing things up :D
Kasmir: That book is intended for graduate students.
It's not written for beginners at algebra.
But it seems to get used that way.
but this is our first course on abstract algebra
like litterly the first time we see what a group is
And that is the required textbook?
23:41
Hmm ...
they make things allways harder
you remember that analysis things I asked you about?
those were second analysis course
I don't remember
thats when I ifirst met u :D
greens theorem
and stokes
The multivariable calculus stuff was all computational.
I passed that course because of your help =p was never gonna get it on my own
23:43
Some of the computations were arbitrarily hard, but they were just computations.
we had to take proofs part as well
Yeah, but the proofs for that and complex variables were totally reasonable proofs.
if you fail 2 questions of the proof
you wont pass even if you get all the computations right
Some year you should watch my lectures, though :)
Haha I did =p but maybe 5 of them only
23:44
Yes, but those proofs were totally fine and not too hard and also reasonably important.
where you defined double integrals
You are very good proffesor, like its not boring being there at classroom
many teachers just write stuff and then claiming that they are avious
I'm just saying it would be good to make sure you get all the linear algebra and basic analysis that's there.
like send me the course on a papper and let me read it at home :D
What do you mean ?
there where?
in those lectures
23:46
anyhow, go back to algebra
Was unlucky for me because took linear algebra first year and did not find those lectures =P
Okay :)
@TedShifrin i got question about image of a function and preimage
the image I get , the elements that our function hit
preimage should be the same thing imo
because f' will act on those to send them back
or what is am missing?
No, the function need not have an inverse — it might not be one-to-one.
By definition, $f^{-1}(C) = \{x\in A: f(x)\in C\}$, if $f:A\to B$ and $C\subset B$.
so image and preimage are the same for 1-1 functions?
and how can we talk about the inverse function if we dont have 1-1 and onto
thats one thing that was not clear, and other was , if a function has left inverse its 1-1
and if it has right inverse it must be onto
I just told you what preimage means. The notation there does not mean inverse function.
Can you please clear those things up ? they were in chapter 0 =P
oh not inverse then its a back map ?
23:53
You should have learned this in an introduction to proofs course, but I guess you didn't take one.
I am so tempted to explain $f^{-1}$ in terms of functors...
We dont have such course
IF $f$ is a one-to-one function, then the preimage is the same as the image of the inverse.
:P jk don't think about it like that
okay that part is clear
23:54
Kasmir: I think I recommended a book to you ages ago. I'll recommend it again. Look at How to Think Like a Mathematician by Houston.
You did not and thank you :D
I'm sure you can find plenty on-line, too.
the problem is that I got many gaps in my knowledge
Like I can do difficult stuff
and I cant do easy stuff at the same time
I competed in olympiade math in highschool
I put an 8 page summary of basic sets, functions, and equivalence relations as an appendix for my algebra book.
Got like 27 /50
23:56
That means you were clever, but not necessarily good at formalities in math :P
haha =p I like how you said "were"
I'm talking about competing in the olympiad.
Ehm Is there a way to buy books so that they come in a week ?
Yes I was just joking
Kasmir: Send me an email.
@TedShifrin What should I put in that email ?
23:58
Nothing ... just enough so it doesn't go to spam.
Okay let me find your email :D
okay is it ok if I put your email on chat?
just to make sure I igot it right?
I can delete the message after

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