I am Den Ducoff, the curator of the Lean Notes wiki. My main collaborator and my best tutor ever is `Gemini 3.5 Pro`. ![[Den Medium.jpg|268]] ![[Den and Gemini.png|232]] [Send dducoff an email](https://tally.so/r/rjQYWL) ## Beginner Lean student ## Retired tutor in Algebra, PreCalculus, Calculus - 30 years of tutoring experience - Certified Math Substitute Teacher in the Boulder Valley School District - Math Tutor for advanced subjects at Front Range Community College, Westminster, Colorado - BA in Math with additional graduate work in math and computer science - Teach once ... learn twice --- ![[Appendix/Media/Icons/Den's Mineral King Hike.jpg|526x296]] [A short video of my epic hike in the Sierra Nevadas near Mineral King](https://www.youtube.com/watch?v=C9TLVovr14A) ![[Den commencement.png|648]] [I gave this commencement talk at the 2022 graduation ceremony for the math department at the University of Colorado, Boulder.](https://www.youtube.com/watch?v=lo-qONv4QVk) --- **Author:** [[dducoff]] **Creation Date:** 2026-06-25