picasso
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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 $\| x \star y \| = \| x \| \| y \|$. deleted 7 characters in body 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