#math - Wed 7 Mar 2007 between 00:00 and 00:47

NY Lost Funds



TRWBWnoway-: is this the same problem as yesterday?
noway-Yes :-/
http://www.mathbin.net/8735
Should I use the fact that every element of A is also a subset of A. Then since P(A) is all the subsets of A, every element in P(A) will a set with elements from A. Then relate the two?
will be a*
TRWBWnoway-: s in P(A) implies s sub A. that's just the definition of P(A). x in S sub A => x in A => x sub A from the hypothesis. x sub A => x in P(A), again by definition of P(A). so x in S => x in P(A), which implies S sub P(A)
noway-: i think the key thing here is to see: S in P(A) <=> S sub A. they are completely the same thing.
noway-ok
is see it more clear now, thank you
TRWBWnp
noway-the second part, x in S sub A => x in A => x sub A, was kinda catching me up a bit
raz0number E-12 is number * 10^(-12), isn't it?
LoganCapaldousu.
raz0got it
korokercyr, i'm here
prettytoneyHi.
Did that guy prove his set theory thing?
kercyrThere is a countable abelian group where every element has order 2.
koroyeah i saw the backlog
prettytoneyHe was on earlier, I forget the question exactly. S \in P(A) => S \subset P(A), where P is a power set.
koroso it's not true that every abelian group of order 2 is isomorphic to Z_2^n for some n?
kercyrright.
koroer, with every element of order 2 i mean
TRWBWPRETTYTONEY: he had been working on it for 2 days so i gave him the answer. i ran out of hints.
prettytoneyhaha, ok.
kercyrBut it's true that the group is isomorphic to a direct sum of Z_2's.
Knight_LordCan I numerically compute df/dx^2 without computing df/dx?
korooh?
Knight_LordFrom a 2D function
koroi thought Z_2^n was the same as Z_2 + ... + Z_2 (n times)
whatever that means when n is infinite
TRWBWkoro: think of operating over P(R) with A+B=C given by C=(AuB)-(AnB)
kercyrZ_2^n is the set of functions from {0,1,..., n-1} to Z_2.
Knight_LordHow to compute df/dxy numerically?
korokercyr: oh so direct sum means with all but finitely many coordinates being nonzero?
kercyrright.
prettytoneyHow did it go, trwbw? Got a hint for me?
kercyruh...
TRWBWkercyr: given any set S, that operation i gave over the powerset of S is isomporphic to Z_2^S
korooh well i told you my algebra was shitty

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NY Lost Funds