An electric dipole is placed at the origin `O` and is directed along the `x`-axis. At a point `P`, far away from the dipole, the electric field is parallel to `y`-axis. `OP` makes an angle `theta` with the `x`-axis then

Explanation

`alpha + theta = 90`
`alpha = 90 - theta`
`tan alpha = tan (90 - theta)`
`(1)/(2) tan theta = cot theta = (1)/(tan theta)`
`tan^(2) theta = 2 rArr theta = tan^(-1) (sqrt(2))`
Note : `tan alpha = (1)/(2) tan theta`