13:53

When term-by-term differentiation is illegal.

20:33

a quaternion version of Euler's formula

19:05

Absolute Infinity - Numberphile

21:16

The most interesting differential equation you have seen.

22:37

Hyperreal Numbers: An Introduction to Infinitesimals and Nonstandard Analysis

14:06

Surreal Numbers (writing the first book) - Numberphile

14:28

one of the most important ideas from Complex functions

16:59

The Hyperreal Number System (and simplifying limit calculations)