Answer
Relative to the positive direction of the x- axis, the direction of the electrostatic force on particle 2 due to particle 1 is $-10.3^{\circ}$
Work Step by Step
Since particle 1 and particle 2 have opposite charges, the electrostatic force on particle 2 due to particle 1 is in the direction of particle 1 from particle 2.
We can find the angle $\theta$ of the electrostatic force below the positive x axis:
$\theta = tan^{-1}~(\frac{1.0~cm}{5.5~cm})$
$\theta = 10.3^{\circ}$
Relative to the positive direction of the x- axis, the direction of the electrostatic force on particle 2 due to particle 1 is $-10.3^{\circ}$
