Testing for coplanarity can be done by finding
the point-plane
distances of the points <span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
<span>
</span></span></span></span></span></span></span></span></span></span></span></span>
<span>
</span></span></span><span>
</span>, ..., <span>
</span> from the plane determined
by <span>
</span> and checking if they are all zero, by using arbitrary
number of <span>
</span> points <span>
</span>, ..., <span>
</span>. Two lines will not always share all planes, though. They can
be coplanar on the same horizontal plane, for example, but not be on the same
vertical plane.
In this problem, we can see that the line WY is obviously in
both planes, and there won't be any additional points unless the planes are
coincident. In this case, since W, X, Y and Z are not all coplanar, the
planes don't coincide, so the answer is Line WY.
