A mass of 10 kg is suspended vertically by a rope of length 5 m from the roof. A force of 30 N is applied at the middle point of rope in horizontal direction. The angle made by upper half of the rope with vertical is $\theta$ = tan^$-$1 (x $\times$ 10^$-$1). The value of x is ____________.

(Given, g = 10 m/s²)