This document serves as my notes of the online lectures on Asymptotics & Perturbation Methods delivered by Prof. Steven Strogatz. These are techniques for solving complicated problems approximately by exploiting the presence of a small or large parameter. These methods can be applied to integrals, ordinary differential equations (ODEs), partial differential equations (PDEs).

These notes have not been proofread by anyone other than myself and readers are advised to be wary of errors. I will periodically make improvements to this document by fixing typographical errors, adding skipped steps, new methods related to, but not covered in, this course (will go into the Appendix).

The source codes/files used to generate various plots and schematics have been made available openly through this GitHub repo. If you wish to contribute to this document, please open a pull request.

Thank you and happy reading!