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I hereby authorize whoever it may concern to post my comments as answers if they wish, whether as community wiki or otherwise if you like imaginary internet points.


Jul
2
comment Find if a point lies in all given circles
@Steven: I'm afraid not, but I wouldn't be surprised if it were exponential.
Jul
2
comment Why is Volume^2 at most product of the 3 projections?
The problem has been posed here previously, but since this question is specifically asking for a simple proof, I would not vote to close as duplicate.
Jul
2
awarded  Curious
Jul
2
comment Characterization of sphere.
It's nothing to be embarrassed about if you have a conceptually clear question but are unfamiliar with the proper notation; you should just write your question in conceptual terms that you are comfortable with. It's perfectly possible to write a good mathematical question with little or no formal notation, and anyway an excess of notation can be just as hard to read as it is hard to write.
Jul
2
comment How do you call a scale that starts at $∞$, has $1/n$ divisions and tends to $0$?
I would guess "reciprocal scale". It brings up some relevant-looking hits on Google at least.
Jul
2
comment Characterization of sphere.
Maybe I'm a bit thicker than Eric, but I don't understand your notation. The dot product of $\mathbf a$ and $\mathbf x$ is not the same as the distance between $\mathbf a$ and $\mathbf x$. And in neither case is the set of all $\mathbf a$ such that $\exists\mathbf x\in H:\mathbf a'\mathbf x=0$ the set of all lines intersecting $H$.
Jul
2
comment How to average 3D Scale Vector?
Pretty sure what you actually want is the geometric mean, even though it doesn't match all the examples in your question.
Jul
2
comment Sampling on Axis-Aligned Spherical Quad
Assuming $\phi$ is latitude, pick $z$ uniformly between $z_0=\sin\phi_0$ and $z_1=\sin\phi_1$, and let $\phi=\sin^{-1}z$. The longitude $\theta$ you can pick uniformly between $\theta_0$ and $\theta_1$.
Jul
2
reviewed Leave Open Probability Help Poisson distribution
Jul
2
revised Find if a point lies in all given circles
added 200 characters in body
Jul
2
comment Find if a point lies in all given circles
@Steven: Please see my updated answer. The algorithm doesn't need to try all $\binom n3$ triples.
Jul
2
comment Find if a point lies in all given circles
@Hagen: I've added an expected linear time algorithm.
Jul
2
revised Find if a point lies in all given circles
added 1269 characters in body
Jul
1
answered Division of plane into equal area regions
Jul
1
answered Find if a point lies in all given circles
Jun
30
revised Meaning of math symbol ~
added 8 characters in body; edited tags
Jun
30
comment Meaning of math symbol ~
It means "asymptotic to". For future reference: Wikipedia's list of mathematical symbols.
Jun
30
comment Show that the ellipse and the hyperbola are convex
I'm not sure in what sense one can consider a hyperbola to be convex, unless one only takes the interior of one of its two branches.
Jun
30
comment Is Matrix $A^2$ invertible if $A$ is invertible?
Intuition: Think of the matrix $A$ as a linear transformation. Then $A^2$ represents applying that linear transformation twice. Suppose you start with a vector $x$, apply $A$ once to get $y=Ax$, then apply it again to get $z=Ay=A^2x$. The inverse is a way to get from $z$ back to $x$, which you can do by undoing $A$ twice: from $z$ you get $y=A^{-1}z$ and then $x=A^{-1}y=A^{-2}z$. In short: $x\xrightarrow{A}y\xrightarrow{A}z$ so $x\xleftarrow{A^{-1}}y\xleftarrow{A^{-1}}z$.
Jun
30
comment Draw a function $g$ such that $g$ is defined on the interval $[-9,9]$
@androidguy might have an easier time looking up one-sided limits, which is the terminology I'm more familiar with.