What is the definition for Coplanar

Step-by-step explanation:

Here, "co" means "shared."  Two lines are coplanar if both lie in the same plane (in which case there are three possibilities:  the lines intersect in one point, the lines coincide (are one and the same), or the lines never intersect (in which case we call them "parallel."

Suppose we take a look at a three-dimensional space with perpendicular x-, y- and z-axes.  If we let one of these three variables be a constant, then the resulting area is a plane (with two-dimenions).  if we held z constant, then the plane would be the xy plane, and any two lines lying entirely in this plane are deemed to be "coplanar:"  they lie in the same plane.

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