Final answer:
The reference angle for a negative angle of -130° is 50°, obtained by subtracting the angle from 180° and then taking the supplementary angle if necessary. The correct answer is option (a).
Step-by-step explanation:
The reference angle is the acute angle (less than 90°) formed by the terminal side of an angle and the x-axis. When dealing with negative angles, you rotate clockwise from the positive x-axis. To find the reference angle for a negative angle, you would add 360° to the negative angle if it is less than -180°, or you would subtract the negative angle from 180° if it is between -180° and 0°. In the case of -130°, since it is within -180° and 0°, we subtract it from 180° to find the reference angle.
180° - (-130°) = 180° + 130° = 310°. However, since the reference angle must be acute, we take the supplementary angle: 360° - 310° = 50°. Therefore, the reference angle for -130° is 50°, which corresponds to option (a).