Change the scale factor (r) between similar triangles; identify the corresponding parts and establish relationships between them.

• Students will identify corresponding parts of similar triangles.
• Students will use the ratio of similarity to find missing measures in similar triangles.
• Students will relate the ratio of similarity to reductions and enlargements.

• scale factor (ratio of similarity)
• corresponding parts
• reduction
• enlargement
• coincide; coincidental

This lesson involves manipulating the scale factor (r) and observing changes in similar triangles; changing the ratio of similarity; and matching corresponding parts of similar triangles. As a result students will:

• Produce reductions, enlargements, and congruent figures.
• Compare corresponding angles and corresponding sides to be compared.
• Infer the relationship between ratio of similarity (scale factor) and the measures of the sides.