Planes

A plane is a flat surface.  It is made up of at least three non-collinear points.  Some good examples of a plane are:  a table-top, a side of a box, and a piece of paper. A plane is labeled using a capital script letter or by using three capital letters of points that are on the plane being discussed.

The plane above would be named ABC or M.  Even though the plane in the picture looks like a parallelogram, planes extend infinitely in all directions.  Your desktop represents part of a plane.  Imagine that the surface extends out beyond the walls of your room and continues forever. 
We learned that two points determine a line.  Similarly, three non-collinear points determine a unique plane.

Have you ever sat on a chair that wobbled?  The four feet of the chair were not in the same plane!  Photographers use tripods to keep their cameras from wobbling since the three feet of the tripod form a unique plane!

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