Answer:
[tex]\frac{5\pi}{6}, \frac{13\pi}{6}[/tex]
Step by step
Remember, a reference angle is a positive acute angle that represents an angle θ of any measurement.
a)
[tex]\frac{3\pi}{6}=90^\circ[/tex], then its reference angle is [tex]\frac{\pi}{2}[/tex]
b)
[tex]\frac{5\pi}{6}=150^ \circ[/tex] is in the second cuadrant, then its reference angle is [tex]180^ \circ -150^{\circ}=30^{\circ}=\frac{\pi}{6}[/tex]
c)
[tex]\frac{13\pi}{6}=390^\circ=360^\circ+30^\circ[/tex], then it is in the first cuadrant and the reference angle is [tex]30^\circ =\frac{\pi}{6}[/tex].
d)
[tex]\frac{8\pi}{6}=240^\circ[/tex] and it is in the third cuadrant, then its reference angle is [tex]240^\circ -180^\circ=60^\circ=\frac{\pi}{3}[/tex]
