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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 …
2026全新重庆旅游攻略——详细心得分享（保姆级攻略、省时省心省钱…
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 …
arithmetic - Formal proof for $(-1) \times (-1) = 1$ - Mathematics ...
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 …
algebra precalculus - Prove $0! = 1$ from first principles ...
How can I prove from first principles that $0!$ is equal to $1$?
如何打•？ - 知乎
如何在输入法里输入这个符号？Google了很多发现都不对
1-1+1-1+1-1+1... 这个无穷数列的值是什么？如何证明？ - 知乎
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 …
Why is $1/i$ equal to $-i$? - Mathematics Stack Exchange
May 11, 2015 · Why is 1/i 1 / i $1/i$ equal to −i i $-i$? Ask Question Asked 11 years, 2 months ago Modified 1 year, 6 months ago …
Why is $x^{-1} = \\frac{1}{x}$? - Mathematics Stack Exchange
Substitute a by 1 and b, c by x, we find both definition of 1 x and x − 1 reduce to the unique y in Y (if exists) such that yx = 1 = xy. As …
False Proof of 1=-1 - Mathematics Stack Exchange
Aug 24, 2016 · Oh, it sounds like Ivm asking those questions rhetorically. I'm not. They are very subtle and difficult questions. Ponder …
What would base $1$ be? - Mathematics Stack Exchange
Apr 25, 2013 · $1={1}^{2}={1}^{3}=\cdots$, so that the 0 0 $0$ is a redundant symbol. The use of it in the unary system does not …