Q. The angle between any two diagonal of a cube is
BITSATBITSAT 2014
Solution:
for a unit cube unit vector along the diagonal
$OP = \frac{1}{\sqrt{3}} (\hat{i} + \hat{j} + \hat{k})$
unit vector along the diagonal
$CD = \frac{1}{\sqrt{3}} (\hat{i} + \hat{j} - \hat{k} )$
$\therefore \cos \theta = \frac{1}{3} ( 1 + 1 -1 ) = \frac{1}{3} $
$ \therefore \tan \theta = 2 \sqrt{2}$
