Distance of the charge from the origin = d=
The electric field strength is in the direction of Ф where
Tan Ф = 30 cm/ 30 cm = 1 => 45 deg. with X- axis.
Cos Ф = 1/√2 and Sin Ф = 1/√2
Since E is negative, the Ф is in the 3th quadrant. ie., Ф = 180+45 deg. = 225 deg.
The vector form of electric field =