The power factor of the circuit shown in fig. is

Total resistance, R = 40 + 40 = 80$\mathrm{\Omega }$. The impedance of L-C-R circuit is given by
$\begin{array}{l}\mathrm{Z}=\sqrt{\left[{\mathrm{R}}^2+{\left({\mathrm{X}}_{\mathrm{L}}-{\mathrm{X}}_{\mathrm{C}}\right)}^2\right]}\\ =\sqrt{\left[(80{)}^2+(100-40{)}^2\right]}\\ =\sqrt{\left[(80{)}^2+(60{)}^2\right]}=100\end{array}$
Power factor, $\cos \mathrm{\theta }=\frac{\mathrm{R}}{\mathrm{Z}}=\frac{80}{100}=0\cdot 8$