Thanks to all of you who support me on Patreon. You da real mvps! $1 per month helps!! 🙂 https://www.patreon.com/patrickjmt !! Deciding if Lines Coincide, Are Skew, Are Parallel or Intersect in 3D. Here I describe two lines in 3space using parametric equations. We have to decide if they coincide, are parallel, are skew or if they intersect in exactly one point.