Barycentric Coordinates
Points, lines, and circumcircle tangents
A method note on homogeneous barycentric coordinates, the circumcircle equation, and tangent lines obtained from their linear terms.
Methods
Methods
The meaning, derivation, and use of methods for Euclidean geometry. Each note can be read when a proof calls for it.
Directed Angles
Angle arithmetic modulo a half-turn
A consistent convention for angle addition, cyclic quadrilaterals, and collinearity, illustrated by the perpendicular feet in Simson’s theorem.