IN THIS CHAPTER
Sizing up similar figures
Doing similar triangle proofs
Scoping out theorems about proportionality
You know the meaning of the word similar in everyday speech. In geometry, it has a related but more technical meaning. Two figures are similar if they have exactly the same shape.
In this section, I cover the formal definition of similarity, how similar figures are named, and how they’re positioned.
Defining similar polygons
As you see in Figure 8-1, quadrilateral WXYZ is the same shape as quadrilateral ABCD, but it’s ten times larger (though not drawn to scale). These quadrilaterals are therefore similar.
- Corresponding angles are congruent.
- Corresponding sides are proportional.
To fully understand this definition, you ...