Answer
Option (d)
Work Step by Step
The angle $\dfrac{11\pi}{6}$ is in Quadrant IV.
RECALL:
The reference angle of an angle $\theta$ in Quadrant IV is given by the formula:
$\text{reference angle} =2\pi-\theta$
Thus, the reference angle of the given angle is:
$=2\pi - \dfrac{11\pi}{6}
\\=\dfrac{12\pi}{6} - \dfrac{11\pi}{6}
\\=\dfrac{\pi}{6}$
The answer is Option (d).
