zobel network in parallel with a speaker

[copresh1]

a zobel network consisting of a capacitor C and resistance Rc is connected in parallel to a speaker of inductance L and resistance Rl.show that frequency at resonance =1/2pi*Sq rt 1/LC(Rlsquare-L/C ÷ Rc square-L/C)

i have begun by equating the reactive components of the branch currents.
iL=iC
(but i dont seem to get anywhere to the expression what i want)

[berkeman]

Is a zobel network a series RC or a parallel RC? Probably a series RC in parallel with the speaker's series RL?

[copresh1]

it is a RC series connected in parallel with RL.

[copresh1]

i have drawn the phasor diagram ( which i will upload later).
from the phasor diagram i can say that
iLsin thetha=iCsin thetha

[Curious3141]

Hint : Find the complex impedance of the combination. At resonance, the impedance will behave as a pure resistance (the reactive component vanishes).

[copresh1]

i have derived the desired result. the second part of the problem(see atached)i do not know where to start.

[copresh1]

attached diagram