Do khi $f=f_{1}$ hay $f=f_{2}$ thi cuong do dong trong mach cung gia tri hieu dung nen goc lech giua $u$
va $i $ trong 2 truong hop la nhu nhau chi khac nhau ve dau.
Vay goc lech nay la $cos\varphi =\frac{\pi}{6}$
Cuong do dong nhu nhau nen co
$Z_{C1}-Z_{L1}=Z_{L2}-Z_{C2}=R.tan\frac{\pi}{6}=150$
$\begin{cases}Z_{C1}-Z_{L1}=150 \\4 Z_{L1}-\frac{Z_{C1}}{4}=150 \end{cases}$
$<=>Z_{L1}=50$
Dap an $A$