Points G and H are collinear but they do not lie on the same plane. How is this possible?

Hint

Which planes are visible in the figure? How many planes are there in 3D space?

Answer

While points G and H do not lie on either plane or , they are coplanar. If we imagine using GH as an axis, we can swivel a plane around it. That means points G and H actually share an infinite number of planes, even though these planes aren't drawn in the image.