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visits member for 1 year, 4 months
seen 9 hours ago

Dec
18
comment Does this algorithm find prime numbers only?
What made you think 3, 5, and 7 are "fundamental", but all later primes aren't?
Dec
8
awarded  Caucus
Dec
3
comment Cube roots answers
Are you sure you haven't done something else wrong, causing you to think that the answer must be a cube root of 8 when it can actually be something else?
Dec
3
comment Is it possible to simulate a floor() function with elementary arithmetic?
@Mathematician171: <number> refers to one of the types available. Other types include <length> and <time>; the documentation is saying you can't do things like divide by a length or multiply two times. Note that it explicitly says that a calc expression may be used wherever <number> values are allowed, so you can put a calc as the right-hand argument of a division in another calc.
Dec
1
comment Confused on a question on sets and functions
Are you just wondering what (-3, 3) and [-7, 2] mean? Those are open and closed intervals, respectively. [0, 9) is half-open.
Nov
25
comment Probability of no ace in a 6 card hand, given 4 are not aces.
"The probability of getting 5th card as non-ace card & probability of getting 6th card as non-ace card are independent." - no they're not! The probability of getting an ace on the 6th card if you got an ace on the 5th is much less than if the 5th wasn't an ace. Your calculation correctly uses the conditional probability for an ace on the 6th dependent on not getting an ace on the 5th; your explanation is wrong.
Nov
21
comment Monty Hall Problem with Five Doors
"not enough to truly affect the difference" - why not? It seems like you're arguing that the amount of information you receive is small enough that you can neglect it in your analysis, but we're not working with any sort of measurement error or approximation here. Also, the amount of information the door-opening gives you is actually quite substantial.
Nov
20
comment What properties are true for “almost all real numbers”?
There are serious problems with the claim that almost all real numbers aren't definable. See MathOverflow for a better treatment of the subject than Wikipedia. In particular, there are models of set theory in which all real numbers are definable.
Nov
18
answered Recursively enumerable sets: the halting set
Nov
15
comment Why is the pole generally outside the contour loop when its outside the contour loop in 2D?
@JearsonNarvaezRojas: How is this even similar?
Oct
30
comment Can you pick a random natural number? And a random real number?
@AsafKaragila: ...ah. I was implicitly imagining each set came with a priviliged enumeration. The axiom of choice is indeed needed before we can do the diagonal stripey thing.
Oct
29
comment Can you pick a random natural number? And a random real number?
"the fact that the countable union of countable sets is countable depends on the axiom of choice" - are you sure about that? The proof explicitly constructs a bijection from $\mathbb N$ to the union; I'm quite confident the axiom of choice never shows up.
Oct
28
comment Why do oscillating sequences diverge?
@RyanReich: If Ryan stands 5 feet away from Mary, and the gap is not growing bigger, I would not consider Ryan and Mary to be moving apart. Similarly, if Ryan and Mary walk in circles around each other, staying 5 feet apart, I would not say they are moving apart. If Ryan and Mary start 5 feet apart and walk towards each other, approaching but not reaching 3 feet apart, I would not say they are moving apart. The fact that analogous situations with sequences are described as divergent is just plain confusing.
Oct
28
comment Why do oscillating sequences diverge?
"Diverge" ... means "doesn't converge" - which is really unfortunate terminology, because in a non-mathematical context, "diverge" denotes that things are moving apart. "Converge" matches up great with non-mathematical usage, but "diverge" is confusing.
Oct
24
comment How to show that the product of two irrational numbers may be irrational?
"There are uncountably many points on the hyperbola" - do we know that?
Sep
30
awarded  Explainer
Sep
25
comment Is it true to say that “it's not logically possible to prove something can't be done”?
If it were impossible, how would you know? You would be helpless to prove it.
Sep
18
comment Function that is non-zero only at one point.
I feel like if you're going to allow domains other than R, it's awkward not to allow codomains other than R as well. Perhaps the codomain is equipped with the indiscrete topology.
Sep
7
comment Arithmetic mean. Why does it work?
What do you mean by "work"? What are you wondering why it accomplishes? The best guess I can come up with is that you're wondering why multiplying it by the number of elements gets you the sum of the elements, but I don't think that's it, because that's blindingly obvious from the formula.
Aug
22
awarded  Yearling