Line-line Distance
The distance between two skew lines with equations x | = | x_1 + (x_2 - x_1) s x | = | x_3 + (x_4 - x_3) t is given by D = ( left bracketing bar (x_3 - x_1)·[(x_2 - x_1)x(x_4 - x_3)] right bracketing bar )/( left bracketing bar (x_2 - x_1)x(x_4 - x_3) right bracketing bar ) .