There are multiple ways to approach these problems. Try different strategies to expand your personal toolkit.
Use Hint 1 from
Let π = 180° and simplify.
Notice, you do not need a calculator if you divide 180 by 6 as your first step.
Use Hint 1 or 2 from 8-106.
Simplify by factoring out Giant Ones.
Use the second part of Hint 2 from 8-106.
Use Hint 2 from 8-106 or try Hint 3:
See parts (c) and (d).
See parts (a) and (b).