12 Components
Big Ideas
Formative Assessment Lesson
End of Unit Assessments
Browse Components
Big Ideas
Formative Assessment Lesson
End of Unit Assessments
Big Idea:

### Congruent parts of a polygon map to its congruent parts under a rotation or reflection.

1 week

Evidence of Understanding

• describe qualities of polygons
• use examples and non-examples to justify a figure is a polygon
• distinguish irregular and regular polygons using congruent sides and congruent angles
• create and justify all of the lines of symmetry for a regular polygon (use paper folding, drawing, reflective devices, etc.)
• use isosceles triangles to understand qualities about regular polygons
• decompose regular polygons into congruent triangles
• use properties of circles to construct an equilateral triangle
• use properties of circles to construct a regular hexagon inscribed in a circle

• explore congruent parts of regular polygons using lines of reflection and center of rotation
• demonstrate how rotational symmetry and line symmetry carry a polygon onto itself
• describe rotations as preserving congruence (isometry) and orientation
• use tools to justify that the line of symmetry, or line of reflection, is the perpendicular bisector
• construct the perpendicular bisector
• explain that the distance of each point of the figure from the line of reflection (line of symmetry) is the same
• generalize qualities about regular polygons using rotational and line symmetry
• Example: connect lines of symmetry with congruent parts within a polygon and the degree of rotation that carries a polygon onto itself
• specify the reflection or rotation that carries a polygon onto itself
• calculate the degree measures that can carry a polygon onto itself
• use the coordinate plane to write the equation of a horizontal or vertical line that carries a polygon onto itself

Develop conceptual understanding:

polygon, regular polygon, irregular polygon, equilateral, inscribed, rotate, reflect, rotational symmetry, line symmetry, isometry, orientation, line of symmetry, line of reflection, perpendicular bisector

Supporting terms to communicate:

examples, non-examples, congruent, side, angle, triangle, square, pentagon, octagon, preserve, perpendicular, bisect, degree measure, clockwise, counterclockwise

Core Resource

A core resource supports multiple days of instruction.

• Matching Polygons
This incomplete Core Resource is designed to support students in making connections between transformations and polygons.
Resource:
Matching Polygons

This incomplete Core Resource is designed to support students in making connections between transformations and polygons.

All Resources From:
• Unit 1

#### Tools of Geometry

Instructional Routine: Sharing Skepticism

The primary goal of this instructional routine is to support students in constructing and critiquing mathematical arguments.

• Counting Triangles
Students will use transformations implicitly to count the number of shaded triangles in a diagram. During sharing of strategies and through annotation, the transformations used will be made explicit.
Resource:
Counting Triangles

Students will use transformations implicitly to count the number of shaded triangles in a diagram. During sharing of strategies and through annotation, the transformations used will be made explicit.

All Resources From:
• Unit 1