Students often assume that a triangle has a center. But when I question them, they can never give me a definition. "You know, THE CENTER!" they say emphatically as if what they mean is simple and obvious.
It isn't simple and it isn't obvious. Indeed the assumption built into talk of "the" center - the assumption that the center is unique - is false. Triangles have many equally good candidates for a center. We'll study four.
11.1 The Circumcenter and Incenter Theorems
Lecture, PowerPoint, Worksheet
11.2 The Centroid Theorem
Lecture, PowerPoint, Worksheet
11.3 The Orthocenter Theorem
Lecture, PowerPoint, Worksheet
11.4 Ceva's Theorem
Lecture, PowerPoint, Worksheet