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### Mastering the Formal Geometry Proof

Suppose you need to solve a crime mystery. You survey the crime scene, gather the facts, and write them down in your memo pad. To solve the crime, you take the known facts and, step by step, show who committed [more…]

### Sizing Up the Area of a Polygon

Not only can polygons be classified by the number of sides they have and by their angles, but they can also be grouped according to some of their qualities. Polygons can have three personality characteristics [more…]

### Simple and Easy Geometry Tips and Tools

The first rule of life? Life (as well as geometry) can be difficult. But why make it more difficult than it has to be? Do you need help with geometry? Here are 11 tried-and-true tips to make your forays [more…]

### Measuring and Making Angles

On a map, you trace your route and come to a fork in the road. Two diverging roads split from a common point and form an *angle*. The point at which the roads diverge is the [more…]

### Classifying Three Types of Triangles

Triangles are classified according to the length of their sides or the measure of their angles. These classifications come in threes, just like the sides and angles themselves. That is, a triangle has [more…]

### Defining the Radian in Trigonometry

A person's introduction to angles is usually in terms of degrees. You probably have a good idea of what a 45-degree angle looks like. And even most middle-school students know that a triangle consists [more…]

### Discovering Pythagorean Triples

The Pythagorean Theorem is certainly one of the most famous theorems in all of mathematics. Mathematicians and lay people alike have studied it for centuries, and people have proved it in many different [more…]

### Geometry Formulas for Polygons

Polygons, those many-sided objects so popular in geometry circles, are subject to their own formulas that help you find the area and angles of various geometrical shapes. Have a look at the most common [more…]

### Coordinate Geometry Formulas

When you work in geometry, you sometimes work with graphs, which means you’re working with *coordinate geometry.*Becoming familiar with the formulas and principles of geometric graphs makes sense, and you [more…]

### Geometry Symbols

If you’re studying geometry, you’re seeing symbols everywhere — symbols for arcs and angles, lines and triangles as well as symbols for the relationships between lines and angles and so on. Following is [more…]

### Triangle Terminology for Geometry

Triangles are at least a third of geometry (tri = three . . . a little geometry humor). But, seriously, the sides and angles of triangles may have all sorts of relationships to each other, and the following [more…]

### Geometry Formulas for 3-D Objects

You know those big, 3-D movie blockbusters? They’d be nowhere without geometry . . . geometry and those weird glasses. Knowing the formulas for 3-D objects is key in the real world of geometry, and those [more…]

### Geometry Formulas and Rules for Triangles

The three-angled, two-dimensional pyramids known as triangles are one of the building blocks of geometry (however three-cornered they may be). Triangles, of course, have their own formulas for finding [more…]

### Geometry Formulas and Theorems for Circles

Geometry isn't all about pointy angles — there are circles, too. What’s interesting about circles isn’t just their roundness: Become familiar with geometry formulas that help you measure angles around [more…]

### Geometry Workbook For Dummies Cheat Sheet

The helpful geometry symbols, formulas, and principles in this cheat sheet ease your learning curve. Working with geometry means never being bored: You get to work with lines, angles, and arcs; triangles [more…]

### Common Geometry Symbols

Using geometry symbols will save time and space when writing proofs, properties, and figuring formulas. The most commonly used geometry symbols and their meanings are [more…]

### Proof Strategies in Geometry

Knowing how to write two-column geometry proofs provides a solid basis for working with theorems. Practicing these strategies will help you write geometry proofs easily in no time: [more…]

### Formulas for Common Geometric Shapes

Depending on the algebra problem, you'll need to know some geometry. The following represents some of the most common shapes in geometry and their formulas for perimeter, area, volume, surface areas, and [more…]

### What Is a Geometry Proof?

A geometry proof — like any mathematical proof — is an argument that begins with known facts, proceeds from there through a series of logical deductions, and ends with the thing you’re trying to prove. [more…]

### Getting to Know the Five Simplest Geometric Objects

The study of geometry begins with the definitions of the five simplest geometric objects — point, line, segment, ray, and angle — as well as two extra definitions [more…]

### Getting to Know Points

Although individual points have no features, when you group them, you can create several different types of points: collinear, non-collinear, coplanar, and non-coplanar. Each type merits an explanation [more…]

### Getting to Know Lines

There are different types of lines (or segments or rays) or pairs of lines (or segments or rays). You can identify single lines based on the direction they’re pointing [more…]

### Getting to Know Planes

When two geometric planes interact with each other, it is in one of two ways: as parallel planes or as intersecting planes. Here are the definitions for these two types of relationships between a pair [more…]

### Getting to Know Angles

Angles are one of the basic building blocks of triangles and other polygons. There are five types of angles: acute, right, obtuse, straight, and reflex. You see angles on virtually every page of any geometry [more…]

### Getting to Know Angle Pairs

Adjacent angles and vertical angles always share a common vertex, so they’re literally joined at the hip. Complementary and supplementary angles can share a vertex, but they don’t have to. Here are the [more…]