Homogeneous coordinates are just another way of expressing regular coordinates. In a later section below I will describe why they are useful in graphics. In two dimensions the point (x,y) would be expressed with homogeneous coordinates (x,y,1) . In three dimensions, the point (x,y,z) would become (x,y,z,1) in homogeneous coordinates. For now, don't worry about this additional number 1 because it does not change the fact that (x,y) represents a point in a plane and (x,y,z) represents a point in 3_D space. Simply put it quietly at the end of the actual list of coordinates because, as you will see, it will make it easier to manipulate points in a coordinate system.

trigonometric functions sin and cos
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