https://gbm.cocalc.cloud/keir/personal/ 2026-05-21T07:21:25+00:00 https://gbm.cocalc.cloud/keir/personal/ https://gbm.cocalc.cloud/keir/personal/lib/exe/fetch.php?media=wiki:dokuwiki.svg text/html 2025-01-09T22:03:37+00:00 Anonymous (anonymous@undisclosed.example.com) https://gbm.cocalc.cloud/keir/personal/doku.php?id=desmos&rev=1736460217&do=diff Desmos Illustrations Main Page By Keir Lockridge Click the link in the lower right corner of each image to view it in Desmos, where you can read an explanation and perhaps see an animation. GLTs and GCLTs <iframe src="https://www.desmos.com/calculator/7qkfndux0p?embed" width="500px" height="500px" style="border: 3px solid #5482cc" frameborder=0></iframe> Circle Inversion <iframe src="https://www.desmos.com/calculator/v67jkktulu?embed" width="500px" height="500px" style="border: 3px sol… text/html 2025-01-09T17:06:51+00:00 Anonymous (anonymous@undisclosed.example.com) https://gbm.cocalc.cloud/keir/personal/doku.php?id=errata&rev=1736442411&do=diff Fuchs' problem for dihedral groups * P975 L11. The correct formula for $U_{p^{r-1} + 1}$ is $$U_{p^{r-1} + 1} = \mathbf{C}_{p-1} \times \mathbf{C}_{p^r} \times \mathbf{C}^{p-2}_{p^{r-1}} \times \mathbf{C}^{(p-1)^2}_{p^{r-2}} \times \mathbf{C}_{p^{r-3}}^{p(p-1)^2} \times \cdots \times \mathbf{C}_{p^{2}}^{p^{r-4}(p-1)^2} \times \mathbf{C}_{p}^{p^{r-3}(p-1)^2}.$$ * P975 L12. The first equation on this line should read “$\mathrm{d}(U_{p^{r-1}+1}) \geq 1 + (p-1)p^{r-2}.$” text/html 2025-12-18T18:52:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://gbm.cocalc.cloud/keir/personal/doku.php?id=gbgr&rev=1766083979&do=diff Good Basis, Great Results A course guide to Linear Algebra By Benjamin Kennedy and Keir Lockridge * [v1.1 Full Color] * [v1.1 Mostly BW] (for printing) * You want the odd pages on the right and even pages on the left when the book is open in front of you so that the margin notes are NOT in the binding-side margin text/html 2025-10-10T14:07:36+00:00 Anonymous (anonymous@undisclosed.example.com) https://gbm.cocalc.cloud/keir/personal/doku.php?id=ntg&rev=1760105256&do=diff Course descriptions: Number Theory and Geometry Below are descriptions for Math 337: Number Theory and Math 343: Geometry if either were to run AY 26-27. Number Theory Number theory, at its core, delves into the surprisingly rich structure of a familiar and central object in mathematics: the set of positive integers. This investigation has engaged many human minds for several millennia, including the ancient Babylonians who inscribed Pythagorean triples on a clay $x^2 + y^2 = z^2$$x^n + y^n… text/html 2026-02-12T21:47:36+00:00 Anonymous (anonymous@undisclosed.example.com) https://gbm.cocalc.cloud/keir/personal/doku.php?id=start&rev=1770932856&do=diff Keir Lockridge Contact Information Associate Professor Department of Mathematics Gettysburg College Gettysburg, PA 17325 email: klockrid@gettysburg.edu Publications * Fuchs' problem for endomorphisms of non-abelian groups, with Sunil Chebolu. J. Algebra 661 (2025) 545–577. * Fuchs' problem for linear groups, with Jacinda Terkel.