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Jul
30
comment Maximization of sum of functions
Let $a=(1,0)$, $B=I_{2\times 2}$. Then $f(x,y)=x^2/(x^2+y^2)$ is concave in $(x,y)$?
Jul
30
comment What is the highest number that can be got from 4383 by moving exactly 2 matches?
An LED-style 9 is supposed to have the bottom horizontal bar. What you have there looks more like a q.
Jul
30
comment What is the value of $\lim_{x\to 0}x^x$?
No, $x\ln x\ne\ln x+1$.
Jul
29
comment What is the formal negation of the statement “There is much X in Y”.
There isn't much X in Y.
Jul
28
comment How can I use the Bullet-Physics's ray-cast normal to calculate angles for a object to lay on a surface?
Does this previous post answer your question?
Jul
27
comment How can I use the Bullet-Physics's ray-cast normal to calculate angles for a object to lay on a surface?
So... you want to rotate the pizza so that its $z$ axis lies along the surface normal, is that right?
Jul
27
awarded  Revival
Jul
26
revised Is there a good approximation for this?
added 3 characters in body
Jul
26
comment Law of Clavius explained
There are two possibilities: Either $P$, or $\lnot P$. But by the premise, if $\lnot P$, then $P$. So in either case, $P$.
Jul
26
comment Is “imposing” one function onto another ever used in mathematics?
If $g$ is constant this is known as a parallel curve.
Jul
23
comment Functions with real domain but complex range, do they have any use?
In general the result of the Fourier transform is such a function. In fact, elements of the Fourier basis (i.e. complex sinusoids) are examples, as are certain wavelets.
Jul
23
revised Exhibit a smooth map $f : \mathbb{R} \to \mathbb{R}$ whose set of critical values is dense.
deleted 16 characters in body
Jul
23
comment Probability of Punctures for a group of cyclists
Your friend is right: For a group of 10 cyclists, the expected value of the total number of punctures is 2.
Jul
22
awarded  Announcer
Jul
22
comment Convex and conic hull, geometric interpretation
I find that looking at pictures helps. P.S. The conic hull isn't the convex hull of $X\cup\{0\}$, because it doesn't have the restriction $\sum_i\lambda_i=1$. It is the set of all points that lie on any ray from 0 through a point in the convex hull of $X$.
Jul
22
comment Article writing: How to represent a matrix by its elements?
This notation is quite rare in my experience. You could say "$A$ is an $n\times n$ matrix with entries $a_{ij}$" or $$A = \begin{bmatrix} a_{11}&a_{12}&\cdots&a_{1n} \\ a_{21}&a_{22}&\cdots&a_{2n} \\ \vdots&\vdots&\ddots&\vdots \\ a_{n1}&a_{n2}&\cdots&a_{nn} \end{bmatrix}$$
Jul
21
comment Why is the wave equation second order
In some applied fields the PDE is also known as the advection equation.
Jul
21
comment Function Domain of cubic root
Click "Use the real-valued root instead". By default, Mathematica chooses the convention that is compatible with complex arguments.
Jul
21
comment How to describe the degree of symmetry of an object?
Wikipedia has a nice overview.
Jul
21
comment Generate random number according to any equation
<clippy>It looks like you're trying to do inverse transform sampling. Would you like some help with that?</clippy>