i2rms R = e2rms R/Z2….….….please prove...

Z is the total impedance of the circuit that is the effective resistance of the circuit due to capacitor , inductor & resistor.
I_rms=E_rms/Z
that is the meaning of it opr to put it in better words in calulation of root mean square values of current and emf it gets implied the to relate I_rms& E_rmswe use Z
I²_rms=E²_rms/Z
With this we can get the above result.
For more detailed proof of I_rms& E_rmsyou can have a look into NCERT 12^thPhysics book.In there it is beautifully explained.