Question: what is a reference angle?
Answer: Definition of Reference Angle: Let θ be a non-quadrantal angle in standard position. The reference angle of θ is the acute angle θR that the terminal side of θ makes with the x-axis. If θ is in QI, θR = θ If θ is in QII, θR = 180° – θ or π – θ If θ is in QIII, θR = θ – 180° or θ – π