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by Mircea
September 22nd, 2004, 7:38 pm
Forum: Technical Forum
Topic: Clayton Copula
Replies: 7
Views: 176272

Clayton Copula

<t>Check Roger B. Nelsen book “An Introduction to Copulas” for a mathematical presentation of Archimedean family of copulas (Clayton is a member of this family). In finance it can be used for building joint distributions from marginal distributions. A typical example is the single mixture-factor mod...
by Mircea
July 30th, 2004, 2:42 pm
Forum: Programming and Software Forum
Topic: C; pass by value const argument
Replies: 4
Views: 179803

C; pass by value const argument

I notice that in GSL (GNU Scientific Library in C) there are a lot of functions declarations that pass by value const arguments.What is the advantage to use a declaration as Func ( const double x );instead of Func ( double x );?
by Mircea
July 27th, 2004, 1:23 pm
Forum: Brainteaser Forum
Topic: The Matchstick Problem
Replies: 77
Views: 189895

The Matchstick Problem

I agree with Triptaka,In LaTexMay be the author meant shorter over longer. In that case there is a finite solution
by Mircea
July 27th, 2004, 1:05 pm
Forum: Brainteaser Forum
Topic: Question from a software interview
Replies: 20
Views: 185065

Question from a software interview

<t>I agree with Ouyang. The only number is 21200. However I use a different line of reasoning. Since a+b+c+d+e=5, e can be only 1 or 0. 1 cannot be since one of the a, b, c, or d must by 4 and the rest 0 (that is 3 zeros)So e = 0Same, d can be only 1 or 0 1 cannot be since we have at least one 1’s a...
by Mircea
July 26th, 2004, 9:55 pm
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

mat,For me = 1.76084 not 2!!!A proof for this problem was posted on July 15. Dose anybody know a shorter one?
by Mircea
July 20th, 2004, 2:06 am
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

alexanderC,I have a proble with the line 3. Do I read well a^(1/b)=a^(-b)? Then for a=b=2 we will have sqrt(2)=1/4!!!. Cool, but wrong.
by Mircea
July 17th, 2004, 2:58 am
Forum: Brainteaser Forum
Topic: Ropes
Replies: 4
Views: 182920

Ropes

Light first rope at both ends simultaneously and in the same time the second rope at one end.When the first rope had burn completely light the second rope at the other end. or use a watch
by Mircea
July 17th, 2004, 1:03 am
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

alexandreC,I guess the confusion comes from the fact that (a^b^c)^d = a^(b^c*d) and not a^b^c^d. (Hint: a^b^c^d = a^(b^(c^d)) )So if you take the power 1/x on both sides at best you get 2^(1/x) = 2^(1/x) which is OK but proves nothing.
by Mircea
July 16th, 2004, 12:00 am
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

<t>EStealth,You miss the point. So again, if the sequence {f(n)} is convergent with limit b then x=b^(1/b). That was proved since the very first replay.Then the sequence {f(n)} is convergent if and only if b is in (0,e] (that implies x is in (0,e^(1/e)]. This is what is proved.I cannot help you more...
by Mircea
July 15th, 2004, 11:23 pm
Forum: Brainteaser Forum
Topic: Quantum computing quiz
Replies: 16
Views: 182977

Quantum computing quiz

EStealth,For arbitrary finite precision arithmetic try Numerical Recipes and use your home PC.
by Mircea
July 14th, 2004, 11:58 pm
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

<t>My conjecture wasThe eq x^x^x^…=b has a solution if and only if b is in (0,e] and that solution is x=b^(1/b).The proof is in four steps. First we will show that the conjecture is true in (0,1], second that for x=e^(1/e) the limit x^x^x^… exist and is equalt to e, third that the conjecture is true...
by Mircea
July 14th, 2004, 3:02 am
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

<t>Estealth,I guess we got lost on notations. Here is how I understand them. 1. When I see a notation like x^y^z, I understand x^(y^z)2. It is not common to use the notation (x^y)^z since this is equal to x^(y*z) which is a lot more simple. Thus when you posted the problem x^x^x^…=2, I understood x^...
by Mircea
July 13th, 2004, 3:21 pm
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

Estealth,Let’s define the series y_k = x^(x^(x^..) k times. We know how to compute y_kThen, we define x^x^x^… to be its limit (ie lim_(k->infty) y_k ). If (when) the limit exists, it’s a valid question. So, the problem is well defined, as well as the fun
by Mircea
July 13th, 2004, 2:36 pm
Forum: Brainteaser Forum
Topic: "Equation"
Replies: 37
Views: 185678

"Equation"

FV,No offence there, the classification was done below by zerdna.
by Mircea
July 13th, 2004, 12:35 pm
Forum: Technical Forum
Topic: Risk Reversals
Replies: 14
Views: 197103

Risk Reversals

Anthony. I guess you are right. I was suspecting that. Thanks a lot
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