agonic lines

Two or more lines which have no intersections but are not parallel, also called agonic lines. Since two lines in the plane must intersect or be parallel, skew lines can exist only in three or more dimensions. Two lines with equations x | = | x_1 + (x_2 - x_1) s x | = | x_3 + (x_4 - x_3) t are skew if (x_1 - x_3)·[(x_2 - x_1)x(x_4 - x_3)]!=0 .

coplanar | director | Gallucci's theorem | intersecting lines | line-line distance | parallel lines | regulus