Just the critical concepts you need to score high in geometry  This practical, friendly guide focuses on critical concepts taught in a typical geometry course, from the properties of triangles, parallelograms, circles and cylinders, to the skills and strategies you need to write geometry proofs. Geometry Essentials For Dummies is perfect for cramming or doing homework, or as a reference for parents helping kids study for exams. * Get down to the basics—get a handle on the basics of geometry, from lines, segments and angles, to vertices, altitudes and diagonals * Conquer proofs with confidence—follow easy-to-grasp instructions for understanding the components of a formal geometry proof * Take triangles in strides—learn how to take in a triangle's sides, analyze its angles, work through an SAS proof and apply the Pythagorean Theorem * Polish up on polygons—get the lowdown on quadrilaterals and other polygons: their angles, areas, properties, perimeters and much more Open the book and find: * Plain-English explanations of geometry terms * Tips for tackling geometry proofs * The seven members of the quadrilateral family * Straight talk on circles * Essential triangle formulas * The lowdown on 3-D: spheres, cylinders, prisms and pyramids * 10 things to use as reasons in geometry proofs Learn to: * Core concepts about the geometry of shapes and geometry proofs * Critical theorems, postulates and definitions * The principles and formulas you need to know