University of Utah
Geometry: Transformations, Congruence, and Similarity
Rigid motions are to congruence as what are to similarity? Investigate properties of rigid motions and define congruence in terms of rigid motions with the ninth chapter of a 10-part eighth grade workbook series. The lesson then prompts...
EngageNY
What Lies Behind “Same Shape”?
Develop a more precise definition of similar. The lesson begins with an informal definition of similar figures and develops the need to be more precise. The class learns about dilations and uses that knowledge to arrive at a mathematical...
Curated OER
Unit Squares and Triangles
This is an interesting geometry problem. Given the figure, find the area of a triangle that is created by the intersecting lines. The solution requires one to use what he/she knows about coordinate geometry, as well as triangle and angle...
Illustrative Mathematics
Is This a Parallelogram?
If both pairs of opposite sides of a quadrilateral are congruent, is the quadrilateral a parallelogram? This task asks learners to determine the answer and to support their answer with a proof. The resource includes a commentary for...
Illustrative Mathematics
Reflections and Isosceles Triangles
Geometers explore symmetries of isosceles triangles by using rigid transformations of the plane. They complete four tasks, including congruence proofs, which illustrate the relationship between congruence and rigid transformations. The...