I was shocked the first time when I knew Fourier transformtion. It is amazing that nearly any function could be expanded as a sum of simple sine and cosine functions. It is very different from another famous expansion, Taylor expansion. Taylor expansion focuses on one point while Fourier ...
以前(more than 10 years ago ... )上张贤科的代数课的时候,他讲到,如果你能注意到这个等式, ( x 是一个矩阵 ) 那么你就可以发表文章了。这个等式可以用来计算矩阵1-x的逆矩阵。刚巧我最近的一篇关于最大似然拟合的文章中用到了这个等式(参见 https://arxiv.org/abs/1805.03961 或者 J ...