We had to find V(in)/V(out):

V(in)=Impedance*Current

The circuit given is RLC circuit with varying frequency of VOLTAGE(V(in)).

The correct solutions of the question considered

Impedance= Resistance +R(l)+R©

Now that’s the thing I don’t understand

Isn’t Impedance = sqrt(r*r+(R(l)-R©)^2)

Giving V(in)/V(out)=sqrt(r*r+(R(l)-R©)^2)/R©

now this equation will have it’s minima at s=1/sqrt(R(l)*R©)

Resulting in itf= r/R©=r*sqrt(c/l)

I don’t understand where I am going wrong.