JEE Main 2012Annual, Paper 1MathematicsMediumVector Algebra184× since 2002Let a→\overrightarrow aa and b→\overrightarrow bb be two unit vectors. If the vectors c→=a^+2b^\,\overrightarrow c = \widehat a + 2\widehat bc=a+2b and d→=5a^−4b^\overrightarrow d = 5\widehat a - 4\widehat bd=5a−4b are perpendicular to each other, then the angle between a→\overrightarrow aa and b→\overrightarrow bb is :AOption A. π6{\pi \over 6}6πBOption B. π2{\pi \over 2}2πCOption C. π3{\pi \over 3}3πDOption D. π4{\pi \over 4}4πCheckSkip · show solution
