Random

technology, observations, and reflection

The exponential of ... everything?

how far can we use the Taylor series to define the exponential?

14 min read · February 12, 2026 · authored by Jie Chen

2026 · math quantum
How to get the sorted array and indices in Python without importing additional modules like Numpy

the power of lambda functions

2 min read · January 24, 2026 · authored by Jie Chen

2026 · code
A subtly wrong proof that ChatGPT generated

and a counter example provided by the same ChatGPT

7 min read · January 21, 2026 · authored by Jie Chen

2026 · math AI
Distances between two multivariate normals

elementary results complementary to the Matrix Cookbook

5 min read · January 20, 2026 · authored by Jie Chen

2026 · statistics
A few tricks in probability and statistics (3): Poissonization trick

some tricks are well-known while some are less

9 min read · January 11, 2026 · authored by Jie Chen

2026 · probability code