It turns out that the radial approach can also be applied to derive the impedance of a 5-spot TDF, and the impedance for "ID, Radial" are the same as "TDF, Radial" (i.e. Equation 12 also applies to a 5-spot TDF analyzed with radial coordinates). This can be derived following the same approach as in Sec. 2.1.1, except using the lower bound of integration in Equation 5 is 𝐷/2 and 𝐴 𝑐 = 𝜋𝑟𝑏/2. Since a similar derivation was already been shown, it is not repeated.