Answer:
0° to 90°: reference angle = angle ,
90° to 180°: reference angle = 180° - angle ,
180° to 270°: reference angle = angle - 180° ,
270° to 360°: reference angle = 360° - angle .
Explanation:
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 – πThe reference angle of 240° is 60°. To find the reference angle of a given angle, A, with measure x°, we start by adding or subtracting. You can see that the terminal side of the 135° angle and the x-axis form a 45° angle (this is because the two angles must add up to 180°). This 45° angle, shown in red, is the reference angle for 135°.