Book excerpt: CliffsQuickReview course guides cover the essentials of your toughest classes. Get a firm grip on core concepts and key material, and test your newfound knowledge with review questions. From planes, points, and postulates to squares, spheres, and slopes — and everything in between — CliffsQuickReview Geometry can help you make sense of it all. This guide introduces each topic, defines key terms, and walks you through each sample problem step-by-step. Begin with a review of fundamental ideas such as theorems, angles, and intersecting lines. In no time, you'll be ready to work on other concepts such as Triangles and polygons: Classifying and identifying; features and properties; the Triangle Inequality Theorem; the Midpoint Theorem; and more Perimeter and area: Parallelograms, trapezoids, regular polygons, circles Similarity: Ratio and proportion; properties of proportions; similar triangles Right triangles Circles: Central angles and arcs; inscribed angles; chords, secants, tangents; arc length, sectors Geometric solids and coordinate geometry CliffsQuickReview Geometry acts as a supplement to your textbook and to classroom lectures. Use this reference in any way that fits your personal style for study and review — you decide what works best with your needs. Here are just a few ways you can search for topics: Use the free Pocket Guide full of essential information Get a glimpse of what you’ll gain from a chapter by reading through the Chapter Check-In at the beginning of each chapter Use the Chapter Checkout at the end of each chapter to gauge your grasp of the important information you need to know Test your knowledge more completely in the CQR Review and look for additional sources of information in the CQR Resource Center Use the glossary to find key terms fast. With titles available for all the most popular high school and college courses, CliffsQuickReview guides are a comprehensive resource that can help you get the best possible grades.