Everyone learns the number one rule about triangles in high school: the angles of a triangle add up to 180 degrees. But did you know that sometimes they don't? Triangles are much more interesting than ...

Big Idea – We can describe, measure, and compare spatial relationships. to build on students' knowledge of triangle and to develop students' reasoning with properties of triangle to develop students' ...

THE principal novelties in this tract are the chapters on the orthopole (with some original propositions by the author) and on orthogonal projection (mostly after Prof. Neuberg). A pretty theorem in ...