The angle between any two diagonals of a cube is Cos−11t. Then value of tt is

Two diagonals OP and CSOP→ direction  ratios are  1,1,1CS⇀ direction  ratios are 1,1,-1if θ is the angle  between two diagonals OP and CS thencosθ=1.1+1.1+1112+12+12.12+12+−12                  =1+1+133                  =13⇒       θ=cos−113it gives  t=3⇒tt=33=27