"i 1 zero":
It shows that the parallel branches of C 1 and L 1 have parallel resonance and infinite impedance. Therefore, "i 1 is zero", but the current of each branch of C 1 and L 1 is not zero, but the magnitude is equal and the phase difference is 180.
Therefore, if ic 1 is needed, we need to know the partial voltage of us in the series circuit of C2 and R2 in the outermost single loop, and divide this voltage by the complex impedance of c 1.
"us is in phase with current I":
The results show that in the outermost ring, L2 and C2 resonate in series, and their complex impedance is zero. In this way, the current I only depends on the series connection of resistors R 1 and R2, and the voltage and current are in phase. As long as the current I is calculated and multiplied by the complex impedance of C2 and R2 in series, the voltages across the parallel branches of C 1 and L 1 can be obtained, and ic 1 can be obtained.
Given the frequency and C2, L2 can be easily found by using the resonance frequency formula.