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 Sep 27 awarded Editor Sep 27 revised Are mathematical articles on Wikipedia reliable? edited body Sep 24 awarded Autobiographer Apr 10 answered Are mathematical articles on Wikipedia reliable? Jan 14 comment Splitting a sandwich and not feeling deceived @JohnU This is why a common version of this problem involves gold diggers or bandits, and a sack of gold powder. Nov 9 comment How to put 9 pigs into 4 pens so that there are an odd number of pigs in each pen? While I appreciate the clever tricky answers, wouldn't community wiki be the appropriate label for this question? Oct 3 comment Literary statements that are false as mathematics While a nice question, shouldn't it be Community Wiki? Jul 28 accepted What form does a function take which desribes a linear coordinate system as seen through a perspective projection? Jun 13 awarded Critic May 15 comment Advocating base 12 number system Actually, the base 12 number system seems to have been common in the past, exactly due to 12 having many divisors. We even have traces of it in many languages (eleven and twelve, not oneteen and twoteen) Mar 14 comment On prime numbers If such a formula existed (which generates a bigger prime from any known prime), then we could generate arbitrarily large prime numbers, and there would be no sense in searching for even bigger and bigger primes. Mar 14 comment On prime numbers @JackM : there might be more than 48, we only know 48 of them. Actually, until a few weeks ago, we only knew 47. Mar 8 comment What was the first bit of mathematics that made you realize that math is beautiful? (For children's book) This is not a proof, this is THE proof of the Pythagorean Theorem. If you traveled back in time, and told Pythagoras himself that $a^2 + b^2 = c^2$, he either wouldn't understand you, or (after you defined what the square root means) wouldn't believe you. Jan 28 comment Funny thing. Multiplying both the sides by 0? With the same trick, you could also prove that 1 = 2 because 1 × 0 = 2 × 0. This might make you understand better why it's wrong. Dec 16 comment Why don't we define “imaginary” numbers for every “impossibility”? We have, for example, x=1/0 if we extend the real numbers by adding infinity, and we specify 0 as -0 or +0 depending from which direction we take the limit. Dec 1 asked What form does a function take which desribes a linear coordinate system as seen through a perspective projection? Dec 1 comment Is there a simple way to turn a coordinate system “inside out”? Actually, I should forget the parabola. As $a$ and $d$ are nearly identical (based on empiric data), it seems the function is nearly linear near the origin. I wonder what can it be... Nov 30 comment Is there a simple way to turn a coordinate system “inside out”? Maybe I'm too tired and don't see what the problem is, but your solution gives a convex parabola instead of the rotated one. You write $x=py^2+qx$ but use it as $x=py^2+qy$ Nov 30 comment Is there a simple way to turn a coordinate system “inside out”? If the origin was moved to $(a,d)$ then $g(b) = e$, not $d$ Nov 30 comment Is there a simple way to turn a coordinate system “inside out”? by the way, shouldn't it be $b=pe^2+qe$ ?