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Aug
20
comment Is there a name for a general upper triangular hollow matrix?
Of course ! :-) thanks.
Aug
20
revised Is there a name for a general upper triangular hollow matrix?
added 48 characters in body
Aug
20
asked Is there a name for a general upper triangular hollow matrix?
Aug
18
comment About a limit-no l'hospital or derivatives
@picasso wake up brain ! :-)
Aug
18
comment About a limit-no l'hospital or derivatives
Could expanding the power series of $e^{\cot (\pi x)\log x}$ help? Just a thought...
Aug
18
comment $\cos \alpha+\cos(\alpha+\beta)+\cos(\alpha+2\beta)+…+\cos(\alpha+(n-1)\beta)=0 $
Ah yes @user1551. I missed the $\equiv$ part ! In fact I didn't see the word "identity" anywhere in the question. I guess it's implied by the context.
Aug
18
comment $\cos \alpha+\cos(\alpha+\beta)+\cos(\alpha+2\beta)+…+\cos(\alpha+(n-1)\beta)=0 $
Maybe $\alpha=\beta=0$ is a special case?
Aug
13
comment Is there a name for this function with properties…
Thanks for clarifying Dietrich, and giving an example of such a system.
Aug
13
asked Is there a name for this function with properties…
Aug
12
comment A name for the property $ \| x \star y \| = \| x \| \| y \| $.
Thanks for the great answer ! When you say "we necessarily assume..." does that mean that if $\mathbb{F}\not\in\{\mathbb{R},\mathbb{C}\}$ then we cannot call $\|\cdot\|$ a norm, so that we must use some other symbol, say $| \cdot |$ and call it something other than a "norm", much like we use the absolute notation for "valuations", for example. And if so, does this $|\cdot |$ have a name in this context ?
Aug
11
comment What is a good book to learn all of prealgebra?
Videos are moving pictures, but if you don't mind that then there are lots of pre-algebra courses on Coursera, for example.
Aug
11
comment What is the value of $-(-6)$?
Given the new context, I think it looks like the "opposite" (which I read as "additive inverse") of $-(-6)$ is the number $x$ such that $x+(-(-6))=0$, i.e. $x+6=0$, i.e. $x=-6$.
Aug
10
accepted Solving $2^x - 3^x + 6^x =0$.
Aug
4
revised A name for the property $ \| x \star y \| = \| x \| \| y \| $.
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Aug
3
comment What does the symbol <<< mean?
Isn't $\ll$ used for "Big-O" notation sometimes ... I seem to remember this from somewhere...
Aug
3
revised Finding a homography in $\hat {\Bbb {C}} $
edited body
Jul
29
revised How to prove $\frac{2^a+3}{2^a-9}$ is not a natural number
added 32 characters in body
Jul
29
revised How to prove $\frac{2^a+3}{2^a-9}$ is not a natural number
added 108 characters in body
Jul
29
revised How to prove $\frac{2^a+3}{2^a-9}$ is not a natural number
deleted 9 characters in body
Jul
29
revised How to prove $\frac{2^a+3}{2^a-9}$ is not a natural number
added 37 characters in body