Given the following two lines, prove that they are parallel, then find the distance between them... (I have circled in red the two parts of the answer which I don't understand. Namely, why are they using the cross-product here, doesn't that give you a value perpendicular to the lines, hence a new vector that is on the parallel planes of the lines? The second part I highlighted I have no idea why they chose this.) Could someone please explain the reasons to me? Something that I could visualize would be helpful. Thanks, prior!