JEE Advance - Mathematics (1992 - No. 2)
A unit vector coplanar with $$\overrightarrow i + \overrightarrow j + 2\overrightarrow k $$ and $$\overrightarrow i + 2\overrightarrow j + \overrightarrow k $$ and perpendicular to $$\overrightarrow i + \overrightarrow j + \overrightarrow k $$ is ...........
$${{\widehat j - \widehat k} \over {\sqrt 2 }}$$
$${{-\widehat j + \widehat k} \over {\sqrt 2 }}$$
$${{\widehat i - \widehat k} \over {\sqrt 2 }}$$
$${{-\widehat i + \widehat k} \over {\sqrt 2 }}$$
$${{\widehat i - \widehat j} \over {\sqrt 2 }}$$