The value of $$\cos 15^\circ \cos 7{{1^\circ } \over 2}\sin 7{{1^\circ } \over 2}$$ is

The smallest positive root of the equation tan x $$-$$ x = 0 lies in

The points ($$-$$a, $$-$$b), (a, b), (0, 0) and (a², ab), a $$ \ne $$ 0, b $$ \ne $$ 0 are always

The locus of the point of intersection of the straight lines $${x \over a} + {y \over b} = K$$ and $${x \over a} - {y \over b} = {1 \over K}$$, where K is a non-zero real variable, is given by