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| bio | website | cobaltduck.info |
|---|---|---|
| location | Milford, OH | |
| age | 41 | |
| visits | member for | 2 years, 9 months |
| seen | 7 hours ago | |
| stats | profile views | 55 |
A former math teacher for 10 years, converted to Software Engineering just a few years ago. Enjoy woodworking, kayaking, hiking, and geocaching.
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2d |
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Why is 987654321/123456789 = 8.0000000729? Unrelated, but ever notice that Sqrt(9.87654321) approximates pi? The number system is full of this kind of stuff. |
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May 12 |
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How to represent the floor function using mathematical notation? What do you mean by that big capital pi with all those other symbols around it? Can you describe that "without words" please? In your accepted answer, what does arctan mean? My point is, all notation was invented to describe some intellectual phenomenon, which may in turn have been based on some earlier idea, etc. until the whole thing ultimately boils down to cavemen telling how many mastadon had been successfully hunted by holding up fingers. |
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Apr 2 |
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Is 1+1 =2 a theorem? The fact that I can describe a system (such as the integers modulo 2) where 1 + 1 = 0, would seem to suggest your statement cannot be a theorem. |
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Mar 21 |
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Is there such a thing as proof by example (not counter example) As a teacher of mine once said: beware Merten's Conjecture! en.wikipedia.org/wiki/Mertens_conjecture |
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Mar 7 |
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What was the first bit of mathematics that made you realize that math is beautiful? (For children's book) Or, more generally, that the ultimate result of this digital summing is the same as the remainder when dividing by 9. |
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Jan 23 |
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“How I wish I could calculate pi” analogs… Citation needed? |
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Dec 31 |
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How to answer a student objection to the use of “of” in pronouncing f(x)? joriki "would have told the student to keep up the critical thinking." However Ben Crowell responds "it's time to grow up to a more mature intellectual level." Very interesting. |
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Jun 22 |
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Tuple definition Have you checked the old stand-by for definitions? en.wikipedia.org/wiki/Tuple |
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Nov 16 |
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Functions over $R$ such that $f(xy) = f(x)f(y)$ There is a term for what you are asking about, 'totally multiplicative function': en.wikipedia.org/wiki/Completely_multiplicative_function |
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Oct 17 |
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Probability that Scouting ashes continue to circulate? So if I am understanding you, a fire may have on the order $10^{26}$ atoms of ash at the end, and I remove about $10^{24}$ atoms. If I model this as a binomial with $n = 10^{24}$ and $p = .01$, then my expected number of atoms from the original fire is $10^{22}$. After two fires, this goes down to $10^{20}$ and so on, until by fire number 12, my expected value goes below $10^{0}$. Makes sense, if my interpretation is correct? |
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Oct 17 |
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Probability that Scouting ashes continue to circulate? @Didier Piau: en.wikipedia.org/wiki/Kolmogorov_zero-one_law (edited question accordingly). |
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Sep 23 |
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How to answer a student objection to the use of “of” in pronouncing f(x)? Andre: Perhaps this is why I no longer teach algebra, and am now a computer programmer! Greg: "When I make a word do a lot of work like that," said Humpty Dumpty, "I always pay it extra." |
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Aug 23 |
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How to determine where the function is continuous and where the function is differentiable with a piecewise function Hint: Is it already clear to you that the function is continuous and differentiable everywhere except possibly 0 and 3, and you simply need to find which properties it fulfills at 0 and 3? |
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Jul 20 |
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probability that point is within triangle formed by three lines of bearing @Christian. Take a compass. Look over it at a landmark. Note the direction of the landmark. This is a reading. Take out your nautical chart and draw a line from the landmark at the reciprocal (i.e 180 degrees) direction. This is the line of bearing. |
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Dec 1 |
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Temporal aberration. Shape of telescope mirror large enough that light transit time is significant If I could clarify, you are seeking a shape such that if two photons strike the mirror at different points but at the same time, then they will arrive at the focus at the same time. Is that correct? |
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Sep 27 |
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Solve cryptogram - ciphertext given I'm not sure what the solution is, but perhaps if the problem were re-worded: There is a phrase that contains 4 words and 22 total letters (not counting the three spaces between the words). One letter appears four times, no letter appears three times, three letters appear twice, and 12 letters appear once each. What is this phrase? |
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Sep 27 |
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Find thickness of a coin "even with a really thick coin it's easier to tilt it when it lands on the edge than when it lands on a face." I have to disagree, consider the case of thickness >> face area, i.e. a dowel rod shape. Here, P(heads) ~= 0, P(edge) ~= 1 |
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Sep 6 |
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Aunt and Uncle's fuel oil tank dip stick problem All: We have a few excellent responses so far, and I have up voted them. Please allow me to leave this one open for a while before accepting an answer. I really am curious what variety of response this will generate. |
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Sep 1 |
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Aunt and Uncle's fuel oil tank dip stick problem Flo and Jim say: This answer is really getting to the heart of the problem (i.e. reducing volume in the cylinder to area under a chord of a circle, reducing to the simplest case then going back and substituting actual values, etc.) But can you tell us how your angle alpha relates to h, the height of the shaded region along a vertical radius? That is how the dipstick will be marked. |
