L4 Reference Angles

A reference angle is the acute angle formed by the terminal side of an angle in standard position and the x-axis.

To find the reference angle for a negative angle, first add 360° (or 2π radians) to the angle until it is positive, then find the reference angle as you would for a positive angle.

50°.

63°.

Subtract 360° (or 2π radians) from the angle until it is within the range of 0° to 360° (or 0 to 2π radians), then find the reference angle.

π/4 radians.

73°.

Yes, they are coterminal angles because they differ by a multiple of 2π.

Reference angle = 180° - θ (or π - θ in radians).

Reference angle = θ - 180° (or θ - π in radians).