- Chapter 5
- Nine Point Circle
- Excircles of A Triangle
- Circumscribed (left) and Inscribed (right) Triangles
- Perpendicular Bisector Theorem
- The Euler Line: The three collinear lines are the orthocenter, circumcenter, and the centroid.
- Angle Bisector Theory: If a point is on the Angle bisector of an angle, then it must be equidistant from the sides of the angle.
- Midsegment Theorem: A midsegment of a triangle is parallel to the non-adjacent side of the triangle, and it's length is half of the length of that side.