Unit 48: Similarity and Congruence

Day 17 of 30

SAS similarity theorem

9-10Mathematics

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Learning Objective

Students will explore sas similarity theorem through guided practice and application.

Today's Lesson

This lesson focuses on sas similarity theorem. Mathematics provides tools for modeling and analyzing complex systems.

Similar figures have the same shape but not necessarily the same size—corresponding angles are equal and corresponding sides are proportional. Scale factor k: ratio of corresponding lengths. For triangles: AA (two angles), SSS (sides proportional), SAS (two sides and included angle proportional). Similarity is used for indirect measurement, scale drawings, and proofs!

As you engage with this material, consider both the theoretical foundations and practical applications. Think critically about how this concept builds on prior knowledge and where you might apply it beyond the classroom.

Challenge yourself to go beyond memorization—seek to understand the "why" behind the processes and principles.

Key Terms
Problem

A mathematical question requiring analysis and solution

Solution

The result obtained by solving a problem

Activities
Instructions
1. Review the example problems for sas similarity theorem. 2. Identify the steps and strategies used. 3. Work through practice problems independently. 4. Compare solutions with a partner.
Materials Needed
  • Notebook
  • Calculator (if needed)
  • Graph paper
Practice Problems
1

Triangles have sides 3,4,5 and 3,4,5. Which congruence postulate applies?

Hint: Three pairs of sides equal.
2

Two triangles have two sides and the included angle equal. Which postulate?

Hint: Side-Angle-Side
3

After proving △ABC ≅ △DEF, what can you conclude about ∠A and ∠D?

Hint: CPCTC

Teaching Tip

For advanced learners: Encourage deeper analysis and real-world connections. Consider extension activities that allow students to apply sas similarity theorem to novel situations.

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