A practical guide to the critical concepts taught in a typical geometry course. Provides the basics you need to score high in geometry, or for parents helping kids study for exams.

Includes index.

An overview of geometry. The geometry of shapes ; Geometry proofs ; Am I ever going to use this? ; Getting down with definitions ; Lines, segments, and rays ; Investigating the plane facts ; Everybody's got an angle ; Bisection and trisection -- Geometry proof starter kit. The lay of the (proof) land ; Reasoning with If-Then logic ; Complementary and supplementary angles ; Addition and subtractions ; Like multiples and like divisions ; Congruent vertical angles ; Transitivity and substitution -- Tackling a longer proof. Making a game plan ; Using all the givens ; Using If-Then logic ; Chipping away at the problem ; Working backward ; Filling in the gaps ; Writing out the finished proof -- Triangle fundamentals. Taking in a triangle's sides ; Triangle classification by angles ; The Triangle Inequality Principle ; Sizing up triangle area ; Regarding right triangles ; The Pythagorean Theorem ; Pythagorean triple triangles ; Two special right triangles -- Congruent triangle proofs. Proving triangles congruent ; Taking the next step with CPCTC ; The Isosceles Triangle Theorems ; The two equidistance theorems -- Quadrilaterals. Parallel line properties ; The seven special quadrilaterals ; Working with auxiliary lines ; The properties of quadrilaterals ; Proving that you've got a particular quadrilateral -- Polygon formulas. The areas of quadrilaterals ; The area of regular polygons ; Angle and diagonal formulas -- Similarity. Similar figures ; Proving triangles similar ; Splitting right triangles with the Altitude-on-Hypotenuse Theorem ; More proportionality theorems -- Circle basics. Radii, chords, and diameters ; Arcs and central angles ; Tangents ; The pizza slice formulas ; The angle-arc formulas ; The power theorems -- 3-D geometry. Flat-top figures ; Pointy-top figures ; Spheres -- Coordinate geometry. The coordinate plane ; Slope, distance, and midpoint ; Equations for lines and circles -- Ten big reasons to use in proofs. The reflexive property ; Vertical angles are congruent ; The parallel-line theorems ; Two points determine a line ; All radii are congruent ; If sides, then angles ; If angles, then sides ; Triangle congruence ; CPCTC ; Triangle similarity.