Problem:

Verify that the vectors <2,3,1>, <1,-1,0>, and <7,3,2> are coplanar.

Question:

Of course, the easiest way to do this is using the scalar triple product. At the time of my test, however, I was unaware of this. I attempted to find the angle between the vectors, and I got the result that the angle did not exist for any vectors I tried. So, if there is no angle between any of the vectors, does it follow that they are coplanar?