Sprint 11 · Chapter 3

The Basic Proportionality Theorem

Understand and apply the Basic Proportionality Theorem (Thales Theorem) to find missing side lengths in triangles.

1. 1Thales and Equiangular Triangles
2. 2Basic Proportionality Theorem
3. 3Visualizing BPT
4. 4Proving the Theorem
5. 5Example 1: Using BPT to find an extended ratio
6. 6Your Turn: Find the missing length
7. 7Calculate AD