Remember that
A complete circle subtends a central angle of 2л radians
so
Applying proportion
Find out how much represent a central angle of 5л/6 radians
1/2л=x/(5л/6)
solve for x
x=(5л/6)/2л
x=5л/12л
x=5/12
therefore
The fraction of the sector is 5/12 of the complete circle
