I am given a question in which I have to find the polarization of the radiated far-zone electric fields when phi is 0 and 90. Why are the following formulas used respectively? For phi = 0 $$ E_\theta = jn\frac{kI_0le^{-jkr}}{4\pi r} cos\theta $$
For phi = 90
$$ E_\theta = jn\frac{kI_0le^{-jkr}}{4\pi r} . 1 $$