Question

I don't get coplanar points? (See attached picture)

I know from the back of the book that 1. B and 2. D and 3. B. No clue how they got there, though.

Answer 1

Coplanar points means that they belong to the same plane.
Imagine four points make up a tetrahedron, they are then not coplanar.
If they are coplanar, they would make a flat solid with no volume.

1. KOGE makes a nice tetrahedron (tent-shaped), so they are not coplanar.
2. GOH happens to be the intersection of a vertical and the horizontal plane, so the three points belong to more than one plane.
3. E and JK form a triangle, which can only belong to a single plane.
A line can belong to more than one plane because if could be the intersection of two planes.

Answer 2

Great thank you :)

Answer 3

You're welcome!