Grade 8Mathematics

Focus: To begin grade 8, students extend their prior knowledge about geometry and geometric measurement. Doing this draws on abilities developed in earlier grades to identify, compose, and decompose shapes, as well as to extend their knowledge to plane figures with different rotation and mirror orientation. Students build on these abilities and their knowledge of geometry to study transformed plane figures. They identify and describe translations, rotations, and reflections, and sequences of these. In describing images of figures on and off square grids and the coordinate plane, students use the terms “corresponding points”, “corresponding sides”, and “image”.

Students learn that angles and distances are preserved by any sequence of rigid transformations and develop a working definition of “congruence”. They experimentally verify the properties of transformations and develop informal arguments showing that alternate interior angles of parallel lines intersected by the same line are equal and that the sum of the angles in a triangle is 180°. This information is applied in later units, including Grade 8 Unit 2: Dilations, Similarity, and Introducing Slope.

Number of Lessons: 17

Lesson Time: Approximately 45 minutes. Please note that each lesson is designed for one instructional block, and may be divided into shorter segments based on teacher pacing and student needs.

Additional Search Terms:

vertex• plane • measure • direction • slide • turn • clockwise • counterclockwise • reflection • rotation • translation • opposite • image • angle of rotation • center of rotation • line of reflection • sequence (of transformations) • distance • coordinate plane • point • segment • coordinates • x-axis • y-axis • polygon • corresponding • measurements • preserve • midpoint • vertical angles • parallel • intersect • congruent • alternate interior angles • transversal • tessellation • symmetry • mathematical practices

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