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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.


8h
comment Infinite Sum of Sines With Increasing Period
You can start a line with an asterisk (*) to make it an item in a bulleted list.
22h
comment verifying the geometric relationship in the Blinn-Phong reflection model.
The only things you need are that (i) the angle between $R$ and $N$ is equal to the angle between $N$ and $L$, and that (ii) the angle between $E$ and $H$ is equal to the angle between $H$ and $L$.
Oct
21
revised Geometric interpretation of mixed partial derivatives?
added 9 characters in body
Oct
21
comment What is $log( b,a)$ according to google?
It appears to be $\log 4.2$. Further reading: en.wikipedia.org/wiki/…
Oct
21
comment Defining ellipse using points and normal vectors from them
You'll definitely need a third point because two points and their associated normals do not determine an ellipse.
Oct
21
comment Defining ellipse using points and normal vectors from them
What exactly is the input? Do you have two or three "gradients" (point-vector pairs) that you know belong to the same ellipse? Or do you just have an unorganized collection of gradients corresponding to several unknown ellipses?
Oct
16
comment Is there a more appropriate SI unit of measure to use to determine the surface area of the playground equipment
The SI unit of area is $\mathrm m^2$. SI does not specify alternative units for use in playgrounds.
Oct
16
comment If -log(f) is convex, is f automatically convex?
Consider $f(x)=\exp(-x^2)$.
Oct
16
awarded  Revival
Oct
15
comment Is $\nabla\cdot{F} = F\cdot\nabla$?
Appropriate user image.
Oct
14
answered Does a unipotent transformation preserve covolume?
Oct
11
comment How to integrate Gravitational force?
en.wikipedia.org/wiki/Classical_central-force_problem
Oct
11
comment Interpolation polynomial Challenge
Say $p(x)=x^2-x^3$. You can match this with a degree-1 polynomial?
Oct
11
revised How to properly use technology for back-of-the-envelope calculations?
edited tags
Oct
10
comment How can I approximate the logarithm of the sum?
Since $b>a$, a better approximation would be $\log b+\log(1+a/b)\approx\log b+(a/b)=\beta+\exp(\alpha-\beta)$.
Oct
10
comment Scalar value of similarity between Two Square Matrices
$\|B-A\|$ where $\|\cdot\|$ is any matrix norm.
Oct
10
comment Can a smooth function $f\colon\partial D^n\to\partial D^n$ be extended to a smooth function $\hat{f}\colon D^n\to D^n$?
Why not $g(|x|)f(x/|x|)$ where $g$ is a smooth function with all derivatives vanishing at $0$, such as $e^{1-1/|x|}$?
Oct
8
comment Geometric interpretation of mixed partial derivatives?
+1 for a very elegant geometric interpretation. However, I'd reconsider your last sentence -- the surface $f(x,y)=x^2-y^2$ is just as saddle-like as $f(x,y)=2xy$ even though the former has $f_{xy}=0$.
Oct
8
revised Calculating the expected winner of a Penney's Game using a Markov Chain.
rolled back to a previous revision
Oct
8
comment How many balls of radius 1 can be packed into a sphere of radius 10?
@Ross: Your link is for circles, not spheres.