Geometry Concepts: GED Test Prep

Updated on Mar 9, 2011

This article reviews the geometry concepts you will need to know for the GED Mathematics Exam. You should become familiar with the properties of angles, lines, polygons, triangles, and circles, as well as the formulas for area, volume, and perimeter. A grasp of coordinate geometry will also be important when you take the GED.

Geometry is the study of shapes and the relationships among them. The geometry you are required to know for the GED Mathematics Exam is fundamental and practical. Basic concepts in geometry will be detailed and applied in this section. The study of geometry always begins with a look at basic vocabulary and concepts. Therefore, here is a list of definitions of important terms.

    area—the space inside a two-dimensional figure
    bisect—cut in two equal parts
    circumference—the distance around a circle
    diameter—a line segment that goes directly through the center of a circle (the longest line you can draw in a circle)
    equidistant—exactly in the middle of
    hypotenuse—the longest leg of a right triangle, always opposite the right angle
    line—an infinite collection of points in a straight path
    point—a location in space
    parallel—lines in the same plane that will never intersect
    perimeter—the distance around a figure
    perpendicular—two lines that intersect to form 90-degree angles
    quadrilateral—any four-sided closed figure
    radius—a line from the center of a circle to a point on the circle (half of the diameter)
    volume—the space inside a three-dimensional figure


An angle is formed by an endpoint, or vertex, and two rays.


Naming Angles

There are three ways to name an angle.

Naming Angles

  1. An angle can be named by the vertex when no other angles share the same vertex: A.
  2. An angle can be represented by a number written across from the vertex: 1.
  3. When more than one angle has the same vertex, three letters are used, with the vertex always being the middle letter: 1 can be written as BAD or as DAB; 2 can be written as DAC or as CAD.

Classifying Angles

Angles can be classified into the following categories: acute, right, obtuse, and straight.

  • An acute angle is an angle that measures less than 90 degrees.
  • Classifying Angles

  • A right angle is an angle that measures exactly 90 degrees. A right angle is represented by a square at the vertex.
  • Classifying Angles

  • An obtuse angle is an angle that measures more than 90 degrees, but less than 180 degrees.
  • Classifying Angles

  • A straight angle is an angle that measures 180 degrees. Thus, both of its sides form a line.
  • Classifying Angles

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