Explanation: In an AC circuit, the power factor is defined as the cosine of the phase angle (θ) between the voltage and the current. This relationship is fundamental to understanding how efficiently power is being delivered to a load. Given a phase angle of 60 degrees, the power factor (PF) is calculated as: PF = cos(θ) PF = cos(60°) PF = 0.5 Therefore, the power factor for an R-L circuit with a 60-degree phase angle is 0.5. Options A, B, and D are incorrect because they do not represent the cosine of 60 degrees. Option B, 0.866, is the cosine of 30 degrees (or sine of 60 degrees).