Assess students’ ability to • give definitions of geometric terms; • make formal geometric constructions (parallel and perpendicular lines); • construct a square and explain why the construction yields a square; • given a geometric figure and a rotation, reflection or translation draw the transformed figure; • understand and explain the formal definition of rotation; • describe transformations as functions; • given a square or trapezoid, describe the rotations and reflections that map it onto itself.
Students construct (with both compass and straight-edge and technology, rather than the physical models and transparencies used in eighth grade) perpendicular lines, parallel lines, and regular polygons, and develop formal definitions of these objects. Students then develop more precise definitions for translations, rotations, and reflections, and use these to describe symmetries - single rigid transformations that carry objects to themselves. Careful attention is given to properties of figures that are preserved (for example, as the result of a translation, a line segment is both parallel and congruent to the pre-image), as they will be important to following work with transformational proofs. Additionally, coordinates are used to represent rigid motions as functions that map points in the plane to points in the plane.