This activity is designed for the students to be active in the lesson.
Students can complete the lesson on paper copies of the coordinate grid or on communicators (available from www.educatorsoutlet.com) or smartpals (available from www.eaieducation.com). The communicators or smartpals are plastic sleeves where students can write on the plastic surface rather than the paper template.
This activity engages students in a five-part lesson:
• Part I: Students graph the vertices of two rectangles and observe that the one rectangle is an enlargement of the other. Students look for a relationship between the corresponding coordinates. They also observe that when a line passes through two corresponding vertices that those lines intersect at the center of dilation.
• Part II: Students graph one quadrilateral and then graph a second quadrilateral whose vertices are three times the original vertices. The students draw lines through corresponding vertices to find the center of dilation. The students observe that the corresponding angles are congruent.
• Part III: Students graph a triangle. This time the students draw a line through the origin and each vertex of the triangle. Students use the dilation lines to draw a new triangle that has sides that are double the original triangle. Students observe if there is a relationship between the corresponding vertices.
• Part IV: Students create a triangle whose one side in on the x or y-axis and whose vertices contain even numbers. Then they create a dilation of the triangle using the scale factor of 1 ½. They then make observations about the lengths of each two corresponding triangles. This time the students also study how the areas of the two triangles are related. They finish by comparing the change in the distances of each vertex from the origin or point of dilation.
• Part V: Students create a new polygon not located at the origin. They name the original vertices and predict the new vertices, before they complete a dilation, that will triple the length of the sides? Then they create a dilation that triples the length of the sides. They also make observations about the area of the two polygons and the corresponding angles.
Comments from Buyers:
• I had to edit the activity for my purposes but it's an excellent guide and was really a "teacher as facilitator" activity.
• Great resource, thanks!
• Wonderful resource. Great for understanding concept.
• Excellent resource. Thanks!