Why does it matter whether we state definitions carefully when we all know what particular geometric figures look like? What does it mean to say that a reflection is a transformation--a function? How does the study of transformations and matrices in high school connect with later work with vector spaces in linear algebra?

How much do you know...and how much do you need to know?

Helping your students develop a robust understanding of geometry requires that you understand this mathematics deeply. But what does that mean?

This book focuses on essential knowledge for teachers...

Why are there so many formulas for area and volume, and why do some of them look alike? Why does one quadrilateral have no special name while another has several, like square, rectangle, rhombus, and parallelogram--and why are all these names useful?

How much do you know ...and how much do you need to know?

Helping your students develop a robust understanding of geometry requires that you understand this mathematics deeply. But what does that mean? This book focuses on essential knowledge for teachers about geometry. It is organized around four big ideas, supported by multiple...