121 reputation
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location Netherlands
age 25
visits member for 3 years, 2 months
seen Dec 18 at 0:38

Jul
12
comment Differentiating $y=x^{2}$
The prevalence of this 'proof by abuse of notation' nonsense has always been baffling to me. How can a mathematician justify dropping all rigor in favor of some logically inconsistent handwaving?
May
30
comment My son's Sum of Some is beautiful! But what is the proof or explanation?
@anaximander: Of course if it were a 6th degree polynomial that would make perfect sense in the 6th grade.
May
14
comment Why is a full turn of the circle 360°? Why not any other number?
Of course that should be 1/2, not 1/4.
May
14
comment Why is a full turn of the circle 360°? Why not any other number?
@Zenon: Personally I think $A = \pi r^2$, $C = 2\pi r$ is nicer than $A = \frac{1}{4} \tau r^2$, $C = \tau r$, if only because it avoids the fraction.
Feb
13
awarded  Teacher
Feb
13
answered Fractions in binary?
Oct
4
awarded  Commentator
Oct
4
comment What's the probability that Abe will win the dice game?
@Bobson: For a d3, wouldn't you normally take a d6 and map 1-2 to 1, 3-4 to 2, and 5-6 to 3?
Oct
1
comment using numbers 1 to 9 only once to equal 1 million
I must have missed the step where base-2 '1000000' equals one million.
Sep
21
comment What is $dx$ in integration?
This is a good explanation of the origin of the notation, but it doesn't quite explain why we bother to write it down. A big part of what the dx notation does is telling you the variable you're integrating over, and as a bonus parenthesizing the integrand. (The latter is probably why the teacher made the 'full stop' remark.)
Jan
21
comment Given a die, what is the probability that the second roll of a die will be less than the first roll?
@Pureferret: Yeah, I agree he could have explained it better.
Jan
21
comment Given a die, what is the probability that the second roll of a die will be less than the first roll?
@Pureferret: Considering that 1/6th of the possible rolls have A = B, 5/6th of the possible rolls have either A > B or A < B. Because of symmetry, half of that 5/6th will be A > B rolls, and the other half will be A < B rolls. Therefore the probability for an A > B roll is (5/6)/2 = 5/12. Does that help? Look at wvnl's answer for a formulaic approach to this reasoning.
Dec
24
comment What do you call numbers such as 100, 200, 500, 1000, 10000, 50000 as opposed to 370, 14, 4500, 59000
@David: I was talking about the OP there
Dec
23
comment What do you call numbers such as 100, 200, 500, 1000, 10000, 50000 as opposed to 370, 14, 4500, 59000
@David: And elsewhere tips are different. It's useless to discuss tips without specifying the cultural situation, so let's not get into that on a question not related to the subject.
Nov
1
comment How to sum this series for $\pi/2$ directly?
@Srivatsan: Yes, of course. Just making a reference to youtube.com/watch?v=OQSNhk5ICTI
Nov
1
comment How to sum this series for $\pi/2$ directly?
@ZevChonoles: Double factorial? What does it mean?! ;)
Oct
23
comment How to prove that $\lim\limits_{x\to0}\frac{\sin x}x=1$?
l'Hôpital's rule is easiest: $\lim\limits_{x\to0}\sin x = 0$ and $\lim\limits_{x\to0}x = 0$, so $\lim\limits_{x\to 0}\frac{\sin x}x = \lim\limits_{x\to 0}\frac{\cos x}1 = 1 $
Oct
17
awarded  Supporter