Find the angle between any two diagonals of a cube.

(i) Find the angle bewteen the lines whose direction ratios are 1, 2, 3 and - 3 , 2 , 1 (ii) Find the angle between two diagonals of a cube.

The vertices of a cube are (0,0,0),(2,0,0),(0,0,2),(0,2,0),(2,0,2),(0,2,2),(2,2,0),(2,2,2) respectively What is the angle between any two diagonals of the cube?

Show that the angle between any two diagonals of a cube is cos^(-1)((1)/(3)) .