The E-feld pattem of an antenna, independent of φ is given as follows:

{ 1/2 0° < θ ≤ 30° }
E = { 1 30° < θ ≤ 60° }
{ 0 60° < θ ≤ 90° }
{ 1/2 90° < θ ≤ 180°}

Find the directivity of this antenna