abstract algebra - Prove that 1+1=2 - Mathematics Stack Exchange
Jan 15, 2013 · The main reason that it takes so long to get to $1+1=2$ is that Principia Mathematica starts from almost nothing, and works its way up in very tiny, incremental steps. …
What does $QAQ^{-1}$ actually mean? - Mathematics Stack …
Apr 28, 2020 · 1 $\begingroup$ When one thinks of matrix products like that, it's helpful to remember that matrices, unlike vectors, have two sets of bases: one for the domain and one …
2025年618哪一款手机性价比高？全品牌、全价位手机推荐与选购 …
Jun 12, 2025 · 1、华为 作为国民品牌的华为，基本上是家喻户晓的，除了华为公司知名度高、实力雄厚之外，它的手机确实很值得称赞。 华为手机不论是是高端机还是低端机，在机子的做 …
有问题，就会有答案 - 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、经验和见解，找到自己的解答」为品牌使命。知乎凭借认真、专业 …
what is 1 - 1/2 + 1/3 - 1/4 + 1/5 - 1/6 + 1/7 - 1/8 +1/9
Nov 28, 2019 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for …
Derivative of sigmoid function $\\sigma (x) = \\frac{1}{1+e^{-x}}$
In my AI textbook there is this paragraph, without any explanation. The sigmoid function is defined as follows $$\\sigma (x) = \\frac{1}{1+e^{-x}}.$$ This function is easy to differentiate
How can 1+1=3 be possible? - Mathematics Stack Exchange
Feb 3, 2021 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for …
2025年 618 电脑配置推荐（配置单可以直接照抄） - 知乎
6 days ago · 2025年618台式机电脑diy配置推荐（这篇文章每月都会更新，可以收藏） 本文内配置单无任何利益相关，配置推荐以性价比为主，每月月初会及时更新，希望大家可以点赞支持一 …
Sum of 1 - 1/2 + 1/3 +.... + 1/n - Mathematics Stack Exchange
One can write $$1+\frac12+\frac13+\cdots+\frac1n=\gamma+\psi(n+1)$$ where $\gamma$ is Euler's constant and $\psi$ is the digamma function. Of course, one reason for creating the …
Mathematics Stack Exchange
Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their …