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3h
comment How write a periodic number as a fraction?
Use the geometric series.
21h
comment Notation for a unit vector
@nosyarg Yes, it's just cleaner.
21h
comment Notation for a unit vector
@nosyarg To clarify that we are talking about the euclidean norm.
22h
answered Notation for a unit vector
22h
answered Creative way to find this area
22h
revised Creative way to find this area
edited tags
22h
comment Show that $\det(A) > 0$
@user1551 Thanks for your patience. I've fixed the error now. I forgot that $A\succ 0$ is only equivalent to $\sigma(A)\subset\mathbb R_+$ if $A=A^T$.
22h
revised Show that $\det(A) > 0$
added 15 characters in body
22h
comment Creative way to find this area
Your illustration suggests you want $y=a$ and not $y=a\cdot r$ as your line...
22h
comment In topology, any relationship on boundary like $Bd(A\cap B)$ and $Bd(A) \cap Bd(B)$?
Maybe if $A$ and $B$ are closed, we can get a little more...
22h
comment In topology, any relationship on boundary like $Bd(A\cap B)$ and $Bd(A) \cap Bd(B)$?
@GregoryGrant Yes, but that's not what the question is asking for anyway. You could answer that there is no inherent relation because both cases, $\subset$ and $\supset$ are possible.
22h
comment fourth derivative
Honestly, it does. See the link from the answer for different schemes for the same derivatives using different numbers of nodes.
22h
comment In topology, any relationship on boundary like $Bd(A\cap B)$ and $Bd(A) \cap Bd(B)$?
@GregoryGrant Bollocks. I was only imagining well-behaved sets. Thanks for pointing out!
22h
comment fourth derivative
How many nodes do you want to use? Do you know how to derive $$f''(x) \approx \frac14(f(x-h) - 2f(x) + f(x+h))~~?$$
23h
revised Show that $\det(A) > 0$
added 38 characters in body
23h
comment How to spline together Bezier curves to form a smoth closed curve?
@so.very.tired You may (this is colloquially called "curvature continuous"). Note that this will take care of one degree of freedom, so you must either sacrifice an interior point per segment for it, or increase the order of the splines.
1d
comment Matrix notation in handwriting
You can draw the letter multiple times above each other. Although what you describes seems more like showing a defect in notation. As the linked quesiton states, you can write without boldface. Usual maths writes matrices and operators as uppercase latin letters, eigenvalues as lowecase greek and vectors as lowercase latin. So if you can, I suggest changing your notation to something more handwriting-friendly.
1d
comment Will decreasing the variance of a subset, the global variance also decrease and vice versa?
How do you want to decrease the variance? Without giving your method, we can't even say if your claim is correct let alone how to prove it.
1d
comment Finding the GCD of two polynomials.
@Sean You can just continue with $-5X+5$. Only when you have the result of the algorithm, you should normalize it.
1d
comment Finding the GCD of two polynomials.
If $P$ is a common divisor, so is $\lambda P$ for $\lambda\in\mathbb R$. You can thus simly scale your result to be monic. Maybe you should show your steps. You may want to use \begin{align*}a^2+b^2 &= c^2 \\ d^2 + e^2 &= f^2\end{align*} for better alignment when doing that: $$\begin{align*}a^2+b^2 &= c^2 \\ d^2 + e^2 &= f^2\end{align*}$$