Geometry — Congruence

About this lesson

This unit introduces the concept of congruence for plane geometric shapes, starting with line segments and angles, then extending to polygons. It emphasizes that congruent polygons have equal corresponding side lengths and angle measures, and that the order of vertices in naming is important. The unit then focuses on triangle congruence, presenting five specific cases: Side-Side-Side (SSS), Side-Angle-Side (SAS), Angle-Side-Angle (ASA), Angle-Angle-Side (AAS), and Right angle-Hypotenuse-Side (RHS). Each case is explained with notation and examples, and students are expected to use these cases to prove triangles congruent and to find unknown side lengths or angle measures in given figures. The unit also includes real-life applications, such as using congruence in bridge construction and fish farming pond design, and exercises that ask students to identify the congruence case used, spot mistakes in solutions, and solve problems involving congruent figures.