歐幾里得與幾何原本 | Euclid and Elements

直線及點的角 | Angles on a Straight Line and Angles at a Point

平行線的角 | Angles of Parallel Lines

平行線的條件 | Conditions for Parallel Lines

三角形的邊角特性 | Properties of Angles and Sides of Triangles

多邊形的角特性 | Angles Properties of Polygons

演繹證明例題 (全等及相似三角形) | Deductive Proof (Congruent and Similar Triangles)

尺規作圖 | Compass-and-straightedge Construction

平行公設 | Parallel Postulate