What would a math book be without a nerdy math joke? Bad joke aside, you might recognize π² as the formula for the area of a circle. And you might infer from that fact that this chapter addresses geometry. Often people think of geometry as a bunch of formulas for finding the area of objects, the volume of objects, and the distance around various shapes. In addition, there are methods for determining how angles and lengths of sides help you make conclusions about the shape of things, and on and on. Unfortunately, that approach alone doesn’t lead to a lot of understanding. This chapter will leave you understanding why the area of a rectangle is the length times the width, why the area of a circle is π², plus much more.