Answer
(a) refer to the image below for the drawing.
(b) $\dfrac{13}{9}\pi$ radians
(c) reference angle = $80^o$ or $\dfrac{4}{9}\pi$ radians
Work Step by Step
(a) From the positive x-axis, move 260 degrees counter clockwise. (refer to the attached image above for the drawing)
(b) Convert to radians by multiplying $\dfrac{\pi}{180^o}$ to obtain:
$260^o \cdot \dfrac{\pi}{180^o} = \dfrac{13}{9}\pi$ radians
(c) The angle is in Quadrant III. The reference angle of an angle $\theta$ in Quadrant III can be found using the formula
$=\theta - 180^o$.
Thus, the reference angle of the given angle is:
$260^0-180^0 = \color{blue}{80^o}
\\=80^o \cdot \dfrac{\pi}{180^o}=\color{blue}{\dfrac{4}{9}\pi}$ radians.
