G-CO.B. Understand congruence in terms of rigid motions

• Are the Triangles Congruent?
• Is this a rectangle?
• Reflections and Equilateral Triangles
• Reflections and Equilateral Triangles II
• Reflections and Isosceles Triangles

G-CO.B.6. Use geometric descriptions of rigid motions to transform figures and to predict the effect of a given rigid motion on a given figure; given two figures, use the definition of congruence in terms of rigid motions to decide if they are congruent.

• Building a tile pattern by reflecting hexagons
• Building a tile pattern by reflecting octagons

G-CO.B.7. Use the definition of congruence in terms of rigid motions to show that two triangles are congruent if and only if corresponding pairs of sides and corresponding pairs of angles are congruent.

• Properties of Congruent Triangles

G-CO.B.8. Explain how the criteria for triangle congruence (ASA, SAS, and SSS) follow from the definition of congruence in terms of rigid motions.

• SSS Congruence Criterion
• When Does SSA Work to Determine Triangle Congruence?
• Why Does ASA Work?
• Why does SAS work?
• Why does SSS work?