[b]1.[/b] Click for point A and B on L1 and L2;[br][b]2.[/b] Click for the directional vectors v1 and v2 of L1 and L2;[br][b]3.[/b] Click for vector joining L1 and L2 i.e. vector a = vector AB;[br][b]4.[/b] Click for vector b the vector product of v1 and v2;[br][b]5.[/b] Click for shortest distance between the skew lines L1 and L2 this is achieved by calculating the scalar projection of vector a onto vector b;[br][b]6.[/b] Move the slider to move point B on L2, notice that the projection does not change;[br][b]7.[/b] Use Rotate 3D Graphics View" to see from different perspectives;[br][b]8.[/b] For full 3D effect: Right click select Graphics - 3D Graphics - Projection - Glasses. Move the view to the right using your mouse and then put on your red-cyan 3D glasses and enjoy.