- The Lost Art of Logarithms (lostartoflogarithms.com)
An online book-in-progress by Charles Petzold wherein is explored the utility, history, and ubiquity of that marvelous invention, logarithms including what the hell they are; with some demonstrations of their primary historical application in plane and spherical trigonometry.
- Octagon (Wikipedia)
In geometry, an octagon (from the Greek ὀκτάγωνον oktágōnon, “eight angles”) is an eight-sided polygon or 8-gon.