Then you're in the right place! This guide to GED geometry will teach you everything you need to know!

In geometry, a plane is a flat, two-dimensional (2D) surface that goes on forever. 

A Plane figure is just a fancy name for a flat, 2D shape that's in a plane. How do you know if a shape is a 2D shape or a 3D shape?

You can usually spot a 2D shape because it'll look like it's flat in the page. This is unlike a 3D shape. 

Here's an analogy. When you're watching a normal movie, you see everything happen in the screen in 2D. When you're watching a movie in 3D, the action looks like it's coming out of the screen at you. Or you just end up getting a headache from wearing 3D glasses (ask me how I know...). 

4-sided plane figures are plane figures with 4 sides. For the GED math test, the 4-sided figures you must know are squares, rectangles, parallelograms, rhombuses, and trapezoids. 

You probably already know what a square looks like. But if it's been a while, don't worry! Just remember this picture. 

Here are the basics you need to know about squares for GED math:

1. All 4 sides of a square are equal in length (this is what the black lines on all 4 sides tell us).

2. A square is a type of rectangle.

3. A square has 4 right angles. There's a right angle in each corner. 

4. A square's opposite sides are parallel (meaning, they are in the same plane but never touch). 

Rectangles are also common shapes that you've probably seen before. 

Be sure you know these points about rectangles for GED geometry:

1. The opposite sides are equal in length.

2. A rectangle has 4 right angles. There's a right angle in each corner (that's what the little box types things in the corners represent). 

3. The opposite sides are parallel (in other words, they are in the same plane but never meet). 

The parallelogram is important to understand for problem solving. It may seem a little more confusing than squares and rectangles, but once you understand a few basic points, you'll see that it's not that bad! 

What to know about parallelograms for GED geometry:

1. For a parallelogram, the opposite sides are the same length. For example, in the picture above, side AB is the same length as DC. Also, side AD is the same length as side BC.  

2. The opposite sides are the same length in a parallelogram.

3. The opposite angles are equal in measure. 

The rhombus is a special kind of parallelogram. 

Don't forget to remember these points about the rhombus for the GED math test:

1. A rhombus has 4 sides that are all the same length

2. The diagonals of the rhombus intersect to form a right angle (this is the little box type thing you see in the center of the rhombus in the picture). 

3. The opposite angles of a rhombus are the same length.