Ben Alpert
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 Jul 30 comment Are the “proofs by contradiction” weaker than other proofs? Related: math.stackexchange.com/questions/198. Jul 30 answered Proof that $n^3+2n$ is divisible by 3 Jul 30 revised Proof that $n^3+2n$ is divisible by 3 added 357 characters in body Jul 30 answered Proof that $n^3+2n$ is divisible by 3 Jul 28 answered How do I convert from Cartesian to conical coordinates? Jul 27 awarded Beta Jul 27 comment Proof of Angle in a Semi-Circle is 90 degrees Nice! Hadn't seen this proof before. Jul 25 awarded Mortarboard Jul 25 comment Probability that two people see each other at the coffee shop Tom Stephens: In Mathematica, you can generate the above plot by running RegionPlot[x - 1/3 < y < x + 1/3, {x, 0, 1}, {y, 0, 1}, FrameTicks -> {{0, 1/3, 2/3, 1}, {0, 1/3, 2/3, 1}}] then selecting Save Graphic As… from the right-click menu to make a PNG. If you don't have Mathematica, you'll need to find some other tool. Jul 25 comment How can I randomly generate trees? And now there's no http://, which you need to make it a link. (I had it in my comment but it was stripped out.) Jul 25 comment Probability that two people see each other at the coffee shop I don't know which classes you're taking where this is a common homework question, but I just really like the graphical solution for this problem and so I thought I'd ask it so that someone could put up the solution. Jul 25 accepted Picking cakes if we need at least one of each type Jul 25 comment Picking cakes if we need at least one of each type I'd always heard this as a "ribbon cutting" problem, but that doesn't seem to be a standard term online. Looks to me like everyone teaches the including-zero variation first, but I find this one much more intuitive. Jul 25 comment Picking cakes if we need at least one of each type This is a variant on Casebash's question that can be solved by changing this problem slightly to fit into that problem's constraints and using that formula, but there's another solution that doesn't require changing the problem. Jul 25 asked Picking cakes if we need at least one of each type Jul 25 comment How can I randomly generate trees? I think that link should just be www-cs-faculty.stanford.edu/~uno/fasc4a.ps. Somehow you got the Google tracking page in there when you copied the link. Jul 25 answered Combinations of selecting n objects with k different types Jul 25 comment Probability that two people see each other at the coffee shop Nice. It's funny we both used Mathematica and then uploaded to imgur for the region plot. Jul 25 awarded Scholar Jul 25 accepted Probability that two people see each other at the coffee shop