Triangles, Part 1: Similar figures and the Basic Proportionality Theorem
Same shape, different size — and the theorem that turns a parallel line into a ratio.
In this lesson you will
- Distinguish similar and congruent figures using equal angles and proportional sides
- State and prove the Basic Proportionality Theorem
- Find unknown lengths in a triangle using the theorem
- Prove two lines parallel using the converse of the theorem