news
About the definition of 'sub-gaussian'
I have a question about the definition of subgaussianity. I have one version of the definition of sub-gaussianity on my textbook here, that is: Suppose ra...
Apr 13, 2026
Archive: News
news
Trig identity $\sin(x)\cos(x) = \sin(2x)/2$?
http://tutorial.math.lamar.edu/Classes/CalcIII/TICylindricalCoords_files/eq0014MP.gif Could someone tell me how $\sin(2x)$ arrives? I know that there is a...
Apr 13, 2026
news
How many "ANGLES" does a pentagon have?
If asked "How many angles does a pentagon have?" would the exterior and interior angles count as 2 angles for each vertex?
Apr 13, 2026
news
What is the sum of all the numbers on the opposite faces of numbers obtained in three rows is?
I have this: A person threw a standard dice three times. He obtained two distinct odd prime numbers in two throws and an even number which is not a factor...
Apr 13, 2026
![Simplifying length of vector $[2\ -4]$](https://news.conceivablytech.com/uploads/simplifying-length-of-vector-2-4_720.jpg)
news
Simplifying length of vector $[2\ -4]$
I understand everything until the last part where they get $\frac{2}{5} \sqrt{5}$? I know the $\lVert [2\ -4] \rVert$ means $\sqrt{2^2 + -4^2}$
Apr 13, 2026
news
Showing bijection by the uniqueness of universal elements.
Let the functor $F$ be $F(S)=S \times S$ (cartesian square). For $A=\{a,b\}$ show $(a,b) \in A\times A$ is a universal element for the functor $F$. Simila...
Apr 13, 2026
news
The order of li(x)
So I've been investigating $\mathrm{li}(x)$, that is the logarithmic integral function. I am unsure if this is true, but it seems as if $\mathrm{li}(...
Apr 13, 2026
news
What is a radical?
It might be too little to care, but there is a term that isn't really defined in a math text, and I was looking if someone could provide a more compl...
Apr 13, 2026
news
if $\omega$ is a primitive cube root of unity then $-\omega$ is a primitive sixth root of unity.
I was given a statement that if $\omega$ is a primitive cube root of unity then $-\omega$ is a primitive sixth root of unity. The roots of $x^n−1$ in $\ma...
Apr 13, 2026
news
Meaning of the word dom.
Let X be a set and $\sum$ a $\sigma$ algebra of subsets of X. Let f and g be real valued functions defined on domains : dom $f$ and dom $g$ $\subseteq X$....
Apr 13, 2026
