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12h
answered Explain “homotopy” to me
Oct
2
comment Each of the two persons makes a single throw with a pair of unbiased dice.What is the probability that the throws are equal?
Are the dice the same color? In short, what is your equals test -- add up the values?
Oct
1
comment Sequence converging to different limits
@Pakk It is just the usual metric on $\mathbb{R}$, with 0 and $\pi$ swapped.
Sep
24
revised What are “instantaneous” rates of change, really?
added 13 characters in body
Sep
21
comment How many fingers do martians have?
Easy. Martians have 10 fingers (in their base, naturally).
Sep
16
answered How do I make a student understand contradiction?
Sep
16
comment How do I make a student understand contradiction?
Except when the proof is fininshed, we have established the falsity of part of the thing we assumed. This does not make the proof by contradiction invalid. You can do a proof by contradiction starting with "assume 0=1", even if you have already established "not 0=1", and it remains valid. It is useless, but valid.
Sep
9
answered I roll a die repeatedly until I get 6, and then count the number of 3s I got. What's my expected number of 3s?
Sep
8
comment Why are all knots trivial in 4D?
Bah, tricky. Can we really have an uncountable number of crossings, and not just infinite? Continuity and compactness should buy us that, no? (been a while) I think I see an attack for a countable number of points with an infinite number of crossings within all neighborhoods. Slide them apart, and then limit as epsilon->0 untangle them.
Sep
8
comment Why are all knots trivial in 4D?
For "Alternatively", could there be an uncountable number of crossings, and would that block that solution?
Jul
27
answered The set of all real functions of a real variable
Jul
22
revised If I buy 2 lottery tickets do I double my chance of winning?
Removed unattributed claims about "Mathematicians" and what "The Internet" says. The entire paragraph didn't add anything to the question.
Jul
22
comment Odds of winning the lottery if I buy 10,000,000 tickets
blogs.scientificamerican.com/guest-blog/… a texas jackpot hit 1.3$ rate-of-return. nytimes.com/1992/02/25/us/… is someone actually doing it. Punchline? Investment theory says even positive ROI tickets are not good investments! maa.org/programs/maa-awards/writing-awards/…
Jul
22
suggested approved edit on If I buy 2 lottery tickets do I double my chance of winning?
Jul
22
comment Why do we show that structures aren't isomorphic by exhibiting a property not shared by one of them?
@MartinBrandenburg "I don't completely agree" doesn't seem to add any useful information: Can you explain what you disagree with, and why, instead of just stating there is something you disagree with? Is this approach not common in different areas of math? Is that phrase not often omitted from proofs?
Jun
12
answered What are “instantaneous” rates of change, really?
Jun
12
comment What are “instantaneous” rates of change, really?
This answer seems to neglect the fact you can use infinitesimals to build a rigorous definition of calculus.
May
26
answered Understanding derivatives
May
14
awarded  Yearling
May
11
answered Why is $1/i$ equal to $-i$?