The radiation field of a certain short vertical current element is E s = (20/r) sin

The radiation field of a certain short vertical current element is E_θs = (20/r) sin θ e^−j10πr V/m if it is located at the origin in free space.

(a) Find E_θs at P(r = 100, θ = 90◦, ϕ = 30◦).

(b) Find E_θs at P(100, 90◦, 30◦) if the vertical element is located at A(0.1, 90◦, 90◦).

(c) Find E_θs at P(100, 90◦, 30◦) if identical vertical elements are located at A(0.1, 90◦, 90◦) and B(0.1, 90◦, 270◦).