crasic
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 Oct 28 comment Two basic question on set theory Using your own logic, how can you get 62 proper subsets out 2^6 total subsets? Why are you subtracting two and not one? Oct 28 comment Two basic question on set theory You could also get there directly, by asking how many subsets you can make out of {2,3,4,5,6} which 2^5 then subtract the one which is the whole set and get 2^5 - 1 = 31 Oct 27 comment How safe is it to ignore low probability events? my point is that in most cases, a MTTF estimate includes a huge number of assumptions about what you know about the system. In a mathematically "closed" problem like SHA-256 you can be confident in these assumptions. But in most cases, multiple failure pathways are overlooked. Oct 27 comment How safe is it to ignore low probability events? If the totalitarian principle is to be believed then everything not forbidden is compulsory Oct 27 comment How safe is it to ignore low probability events? Failure rates estimates are entirely unreliable. take for example, the Space Shuttle. Official stated MTTF is >10K launches. As both Feynman (who was on the Columbia disaster investigation committee) and reality showed, the real number is close to 50. Oct 27 awarded Commentator Oct 27 comment Windows lightweight Math Software @Vojtech It's pretty good for basic plotting. It has a syntax that is pretty much identical to matlab. A lot of people (me included) use it to plot figures for papers Oct 27 revised Windows lightweight Math Software deleted 10 characters in body Oct 27 answered Windows lightweight Math Software Oct 27 comment Do the equations used in Stargate make sense or are they gibberish? I know the equation you are talking about (the one Chloe solved). From what I remember it was a simple integral (I didn't pay too close attention so it may have been improperly written) that any 1st year calculus student can solve. Oct 27 accepted Subgroups of finitely generated groups are not necessarily finitely generated Oct 27 comment Identity involving Euler's totient function: $\sum \limits_{k=1}^n \left\lfloor \frac{n}{k} \right\rfloor \varphi(k) = \frac{n(n+1)}{2}$ What immediately jumps out is how such a complicated function like the totient function has an identity involving the simple summation of integers 1 to n. Seems like a good way to prove it is to show that the expression inside the sum is a "rearrangement" of the sequence of integers 1 to n Oct 27 awarded Supporter Oct 26 comment Are Continuous Functions Always Differentiable? As the last American president demonstrated, every potential threat deserves maximum military action. Oct 26 answered Are Continuous Functions Always Differentiable? Oct 26 asked Subgroups of finitely generated groups are not necessarily finitely generated Oct 15 comment The Hangman's Noose - A Logical Paradox I understand that its an open question and that there is much debate on the topic, no reason not to extend the debate to here. Oct 15 asked The Hangman's Noose - A Logical Paradox Oct 15 accepted Coloring the faces of a hypercube Sep 29 answered How do you define functions for non-mathematicians?