According to the sources, in an AC circuit, the phase angle $\phi$ between the source voltage and the current is given by the relation $\tan \phi = \frac{X_L - X_C}{R}$, where $X_L$ is the inductive reactance, $X_C$ is the capacitive reactance, and $R$ is the resistance . For a phase angle of $45^{\circ}$, the tangent value must be 1 ($\tan 45^{\circ} = 1$), which occurs when the net reactance $|X_L - X_C|$ is equal to the resistance $R$ . In the specific circuit provided in the original NEET 2023 (Manipur) examination, the components are chosen such that this condition is met.