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4h
reviewed Reviewed How to visualize orientation of 3d objects
4h
comment How to visualize orientation of 3d objects
The Wikipedia article on the right-hand rule has some illustrations of the orientations or chirality of coordinate axes in 3D. It might help to inform your discussion of this topic.
4h
reviewed Close Find the line normal to the curve at a specified point
4h
comment Find the line normal to the curve at a specified point
It appears that you have simply copied an exercise for your Readers. While it is certainly allowed to ask for help with assignments, it's expected that you show you've thought about the problem yourself. With that in mind (see How to Ask), please share what approach you took to this problem and what difficulty (if any) you found.
6h
reviewed Close How to reverse $n\log n$?
6h
comment I have to show center of $M_n(H)$ is $\mathbb{R}I$
One direction (of set inclusion) is easy, right?
6h
reviewed Approve Finding the harmonic function at a given point
6h
reviewed Close show or find the adjoint operator of an operator
6h
comment show or find the adjoint operator of an operator
I would start with the definition of the adjoint of a linear transformation (on a Hilbert space, as you say).
7h
comment Is $74*2^n - 1$ prime for some $n$?
Maybe it would be best to back up and explain what you are trying to do.
7h
comment How do we add numbers?
Are you asking about pencil-and-paper algorithms to add large numbers?
9h
reviewed Approve Is the cartesian product associative
10h
comment Is $74*2^n - 1$ prime for some $n$?
@RobertIsrael: The Question was originally posted without $\LaTeX$, so the fact the problem was not stated in simplest form created suspicion on my part that a misunderstanding might creep in.
10h
comment Is $74*2^n - 1$ prime for some $n$?
Perhaps some parentheses are needed to remove ambiguity. As stated it would seem $74*2^n - 1$ simplifies to $37*2^{n+1}-1$.
11h
comment Orientation of a link in a link-system in space
By "link" do you mean a rigid-length segment? If three links have three spherical joints connecting them, do we have a triangle?
12h
comment Which are the operations used in mathematics?
The operations you've listed are (presumably) binary operations, meaning that they act on an ordered pair of operands. More generally operations might be unary (taking one operand), nullary (no operands, so essentially the same as a constant), or $n$-ary (taking $n$ operands for specified natural number $n$). One sometimes encounters ternary operations, though I'm not familiar with higher numbers of operands finding useful applications.
15h
comment The domain of logarithmic functions with sinx and cosx
It might be a little easier to think first about finding solutions in the first period $(0,2\pi)$ and then adding any integer multiple of $2\pi$ to those solutions, rather than carry the periodic framework through the solution process from beginning to end.
18h
reviewed Leave Open If $\sum\limits_{i=1}^{n}a_{i}^{2}=−1$. Show that if $c\in F$ $\exists$ $b_{1}, \dots , b_{k}$ of $F$ satisfying $c =\sum\limits_{i=1}^{k}b_{i}^{2}$.
18h
reviewed Close Let X have density 2t on 0 < t < 1 and Y be uniform on the interval (0, 10) and independent of X. Find the density of Y/X.
18h
reviewed Close Discrete Structures camper problem