I did this short video to try out my new document camera integrated with my Yeti microphone. I held the writing tablet in my lap at a convenient angle, used the adjustments of the camera to "flatten" and rotate the view to make it look right, and took the audio from my Yeti instead of the built-in mic in the camera. I used moderate lighting and all-in-all, I think it turned out pretty well. The content of the video is a proof of the Quadratic formula,... pretty standard derivation which you might find helpful if it meets you "where you're at". Just keep in mind the real significance of this video is as a technical test run, not brilliant pedagogy. ... https://www.youtube.com/watch?v=RmwUjghPSt4

This is part of a series of arithmetic lessons created for my grandkids, but I'm opening them to the world. You can access an annotated index with links on my Math Without Borders website here: https://mathwithoutborders.com/the-grandpa-project ... https://www.youtube.com/watch?v=mDBE5gK88ZU

The Pythagorean Theorem appears in nearly every branch of mathematics. Here are several proofs drawing from algebra, geometry, and trigonometry. ... https://www.youtube.com/watch?v=GsgfP6KZHxg

This is part of the precalculus course in the Math Without Borders Home Study Companion series, based on the third edition of Paul A. Foerster's Precalculus with Trigonometry: Concepts and Applications. For more info on the course, check out http://www.mathwithoutborders.com. Sage is a powerful computation tool. It does symbolic and numerical processing and is useful at the university level and beyond. The main difficulty in using it with high school students is that most of the tutorials include such high-end topics that it is easy to become overwhelmed. This video selects out the matrix and vector topics needed for the work in Chapter 13 of Foerster's textbook, which deals with matrix transformations. I am posting it publicly because as a brief introductory tutorial it may be of interest to others as well. Some level of understanding of matrices is assumed in the explanations. For practice you can download the Sage file shown in the video and interact with it directly here: http://mathwithoutborders.com/wp-content/uploads/2012/07/download_worksheets.zip. Download, then unzip this file to your desktop, then start Sage, then upload the sws file (enclosed in the zip file) from your desktop into Sage. ... https://www.youtube.com/watch?v=GKuYyuBVXoU