**In This Chapter**

Discovering points, lines, and angles

Looking at simple geometric shapes

Investigating the world-famous Pythagorean theorem

It's useful to know a little geometry, and that's what this chapter contains — a little geometry. Geometry is the branch of mathematics that deals with the details of shapes.

Geometry is important because it's conceptual; it improves your thinking. It's part of a full program of math studies, and it has lots of good vocabulary words. And geometry is visual, unlike algebra and trigonometry, so it's easier to grasp. But above all, geometric concepts and words come up in your everyday work.

A flat surface, such as a piece of paper, is called a *plane*, and basic geometry is also called *plane geometry*. You can find other geometries besides plane geometry, such as solid geometry, spherical geometry, Riemannian geometry, Poincaré geometry, and taxicab geometry, which aren't (mercifully) part of this chapter.

In this chapter, you review the basic parts of basic geometry — points, lines, angles, planes, and a coordinate system. And you get the straight skinny about the centerpiece of geometry, the Pythagorean theorem. (Just saying "Pythagorean theorem" makes you feel instantly smarter.)

Start Free Trial

No credit card required