Vector product of two vectors $2\hat i\, + \,\hat j\,$ and $\hat i\, + \,2\hat j\,$ is
If for two vector $\overrightarrow A $ and $\overrightarrow B $, sum $(\overrightarrow A + \overrightarrow B )$ is perpendicular to the difference $(\overrightarrow A - \overrightarrow B )$. The ratio of their magnitude is
Obtain the scalar product of unit vectors in Cartesian co-ordinate system.