知乎，中文互联网高质量的问答社区和创作者聚集的原创内容平台，于 2011 年 1 月正式上线，以「让人们更好的分享知识、经验和见解，找到自己的解答」为品牌使命。

Why is $1$ not considered a prime number? Or, why is the definition of prime numbers given for integers greater than $1$?

How can calculate Laurent series for $$f(z)=1/ \\sin(z) $$ ?? I searched for it and found only the final result, is there a simple way to explain it ?

知乎，中文互联网高质量的问答社区和创作者聚集的原创内容平台，于 2011 年 1 月正式上线，以「让人们更好的分享知识、经验和见解，找到自己的解答」为品牌使命。

Feb 3, 2021 · Hi, welcome to Math SE! Can you show us the proof you're looking at? There are a lot of false proofs of this sort out there, typically involving division by 0, I would imagine that's probably the …

如何在输入法里输入这个符号？Google了很多发现都不对

$1$ is a multiplicative identity and multiplying by 1 1 $1$ is the same as leaving things alone so if xk =x ⋅ x ⋅ x.... ⋅x k times x k = x x x x ⏟ k times

中华人民共和国国家标准 标点符号用法 4.9 括号 4.9.1 括号常用的形式是圆括号“（）”。此外还有方括号“ []”、六角括号“〔〕”和方头括号“【】”。 4.9.2 行文中注释性的文字，用括号标明。注释句子里某些词 …

Is there a formal proof for $(-1) \\times (-1) = 1$? It's a fundamental formula not only in arithmetic but also in the whole of math. Is there a proof for it or is it just assumed?

现在网上关于重庆的旅游攻略大部分都已经过时。有的人出发时查了很多攻略，结果到了重庆还是一头雾水。鉴于此，以我近期去重庆旅游的经历总结出这篇 【全新重庆旅游攻略】，提供给各位。如果你 …