2.30. The normalized far-zone field pattern of an antenna is given by vinth or bi (sin cos² )1/2 0≤0≤ and 0 <≤л/2, 3/2 <≤≤2 E= 0 elsewhere Find the directivity using (a) the exact expression (b) Kraus' approximate formula (c) Tai and Pereira's approximate formula (d) the computer program Directivity of this chapter