EXAMPLE 4
Use reference angles to evaluate functions
b.
The angle            is coterminal
with        . The reference
 angle is θ' = π  –         =          .
The cosecant function is positive in Quadrant II, so you can write: 
17π
6
5π
6
5π
6
π
6
csc           = csc         = 2
17π
6
5π
6