Triangle similarity criteria (AA, SAS, SSS) and proportional sides

What you'll learn

1. State the definition of similar triangles and explain how similarity differs from congruence
2. Apply the AA criterion to determine whether two triangles are similar
3. Apply the SAS and SSS similarity criteria to verify or establish similarity
4. Identify corresponding sides in similar triangles and set up correct proportions
5. Solve for missing side lengths using cross-multiplication
6. Recognize and solve common ACT similar-triangle setups: overlapping triangles, parallel-line cuts, and shadow problems
7. Use the scale factor to find perimeter ratios (k) and area ratios (k²)

Prerequisites

• Classification by sides and angles
• Triangle angle sum and exterior angle theorem