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776190
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location Minneapolis, MN
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visits member for 3 years, 1 month
seen 14 mins ago

I have a Ph.D. with a minor in mathematics and a major in statistics.


22m
revised How to prove $\sum_{i=1}^k(\frac{1}{\alpha_i}\prod_{j\neq i}^k\frac{\alpha_j}{\alpha_j-\alpha_i})=\sum_{i=1}^k\frac{1}{\alpha_i}$?
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23m
revised If $a_i>o$ then $(a_1a_2\cdots a_{2^n})^{1/2^n}\leq \frac{a_1+a_2+\cdots+a_{2^n}}{2^n}$
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25m
revised Codifying ways to think and write about imprecise ideas?
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3h
comment Asymptotic Behaviour Of A Bizarre Function 2
One can write $\lfloor x \rfloor$ and $\left\lfloor \dfrac x n \right\rfloor$. ${}\qquad{}$
4h
revised Heaviside Unit Step Function
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4h
answered Heaviside Unit Step Function
4h
asked Codifying ways to think and write about imprecise ideas?
4h
revised Fourier Series $\sin(\sin(x))$
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5h
revised Can the product of $n$ factorials be $n$ factorial?
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5h
comment Evaluate the area of the region bounded by the ellipse, where is my mistake?
They are used far more generally. To explain why $dy\,dx$ becomes $r\,dr\,d\theta$, I don't think I'd even mention Jacobians. I'd just say that arc length on a circle is radian measure times radius, and the infinitely small increment of radian measure is $d\theta$, and the radius is $r$, so the infinitely small increment of arc length is $r\,d\theta$. It is at a right angle to the infinitely small change in radius, so the infinitely small area is $(dr)\cdot(r\,d\theta)$. Jacobians give the same result, but this bit of geometry should also be understood. ${}\qquad{}$
5h
revised Question about writing proofs for limit
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9h
revised Derivative of a matrix function with respect to a matrix
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9h
revised Checking proof that $f(x)=x^2+1$ is continuous
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10h
revised Permutation Partition Counting
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10h
revised Trigonometry Question: find Value of…
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10h
reviewed Approve suggested edit on Trigonometry Question: find Value of…
11h
revised Density of a random variable as a function of random variables
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11h
comment Density of a random variable as a function of random variables
It is conventional to use the lower-case $f$, as in $f_Z(z)$, for the densisty, and the capital $F$, as in $F_Z(z)$, for the cumulative distribution function $z\mapsto\Pr(|Y-X|\le z)$. ${}\qquad{}$
11h
comment Percentage of primes among the natural numbers
Notice the correct use of \mid, \nmid, and \bigcap. They look different from the way I found them.
11h
revised Percentage of primes among the natural numbers
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