What is the reference angle for a $240°$ angle?

• A. $60°$
• B. $180°$
• C. $270°$
• D. $30°$

Answer: (D)

Verified step by step guidance

1. Identify the quadrant in which the given angle 240° lies. Since 240° is between 180° and 270°, it is in the third quadrant.
2. Recall that the reference angle is the acute angle formed between the terminal side of the given angle and the x-axis.
3. For angles in the third quadrant, the reference angle \( \theta_{ref} \) is found by subtracting 180° from the given angle: \( \theta_{ref} = \theta - 180^\circ \).
4. Substitute the given angle into the formula: \( \theta_{ref} = 240^\circ - 180^\circ \).
5. Simplify the expression to find the reference angle.