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.
Example 2
Which points are not on plane ?
Hint
All you gotta do is look at the picture.
Answer
A, H, I, and E are not on plane .
Example 3
Which points are not on a labeled plane?
Hint
Which points are on neither plane nor ?
Answer
Only I and H are on neither nor .
Example 4
Which points are on both plane and ?
Hint
Two planes intersect at a line.
Answer
B, C, and D are all on both and .
Example 5
What is the best term to describe points I and E?
Hint
They are both part of IE.
Answer
Collinear
Example 6
What is the best term to describe lines BD and IE?
Hint
They're neither parallel nor intersecting. They're on different planes entirely.
or 
, they are coplanar. If we imagine using