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1d
comment Under which branch of mathematics do vectors fall into?
See analytic geometry and linear algebra.
Jan
26
comment Physical meaning of some identity in a weighted undirected graph
How did you come across this equation? Some context might help for finding a meaningful interpretation.
Jan
25
comment The top 1% own 50% of the world's wealth - how do we turn this into a function?
en.wikipedia.org/wiki/Pareto_principle
Jan
24
comment Generating Symmetric Matrix
Any such matrix is of the form $A=Q\Lambda Q^T$ with orthogonal $Q$ and diagonal $\Lambda$, such that the minimum diagonal entry of $\Lambda$ has multiplicity at least $2$. Generate such a $Q$ and $\Lambda$ randomly and you're set.
Jan
23
comment Infinite connected graph such that every vertex has finite degree
Sounds about right. Pick a vertex $v$ and consider the number of vertices that can be reached from $v$ in up to $n$ steps. (I assume a connected infinite graph is one in which any two vertices have a path of finite length between them.)
Jan
23
comment How to Distribute Points in a Poisson Distribution in a Circle
Do you mean a Poisson-disk distribution?
Jan
23
comment Confusion about order of operations with point-in-tetrahedron formula
Here's the easy way to test if a point is in a tetrahedron: steve.hollasch.net/cgindex/geometry/ptintet.html
Jan
22
comment Why can a circle be described by an equation but not by a function?
The standard definition of the square root function is that it evaluates to the positive square root.
Jan
22
comment Basic Differential geometry: Shortest path between two points in R^3 is straight.
Have you tried computing $f'(t)$? What have you got so far?
Jan
20
comment L0 norm, L1 norm and L2 norm
None. You can multiply $y$ by any nonzero scalar and it doesn't change the $L^0$ norm.
Jan
20
comment Optimal size of n circles to fit an area given their relative sizes
Even if all the sizes are equal, this is a pretty tricky problem and no general solution is known: en.wikipedia.org/wiki/Circle_packing_in_a_square
Jan
20
comment Why do transcendental numbers exist?
For your revised question: There are only a countable number of finite sequences of operations.
Jan
20
comment Solutions to $1 - \frac{r'^2}{2c^2} + \frac{r r''}{c^2}=0$?
$1/r^2$ is never zero, so the equation is equivalent to $1-r'^2/2c^2+rr''/c^2=0$, isn't it?
Jan
20
comment What is the exact and precise definition of an ANGLE?
First of all, you haven't actually defined $f$. Is it any function from "corners" to reals? Can I choose $f(abc)=42$ for all $abc$? Second of all, any definition you gave in this framework could not distinguish positive and negative angles, or give a meaning to angles greater than $\pi$, because you've defined a corner just as a set $A\cup B$ with no notion of orientation. So this does not address the confusion expressed in the OP's question.
Jan
20
comment Is it possible to solve the following problem without any coordinate system and if so, how?
You could just draw lines parallel to $\vec{AB}$ and $\vec{AC}$ through the relevant points, and then do the same thing you did with a coordinate system.
Jan
18
comment Can the transpose of a matrix times itself reveal the original matrix
Let $B=AQ$ where $Q$ is an orthogonal $n\times n$ matrix. Then $BB^T=AA^T$, so you cannot recover $A$ from $AA^T$. Similarly, if $C=RA$ where $R$ is orthogonal then $C^TC=A^TA$.
Jan
17
comment Is there any triangle whose circumcenter lies on its incircle?
I added a picture to your answer. Hope you don't mind.
Jan
16
comment Does there exist an explicit formula for the coefficient of $x^k$ in the square of a polynomials?
$\sum_{l=0}^ka_la_{k-l}$, taking $a_l=0$ if $l\not\in\{0,\ldots,n\}$.
Jan
16
comment Is this a legit way to visualize complex functions?
@user1537366: And actually, that's what you get when you rotate around the $x$- or $y$-axes. Rotating around the $z$-axis, like the OP says, just rotates the plot in-plane...
Jan
16
comment Is the Center of Math Wrong?
@Nate: I think they mean that the sequence is the interleaving of two sequences, one in which entries increase by 2 and one in which entries increase by 1.