Trigonometric equations and their solutions

π=pi - format looks like an n =/

sinx=1/2

x=π/6 and x=π-π/6=5π/6

x=π/6+2nπor x=5π/6+2nπ

now the next problem does:

sinx=-1/2

x=π+π/6=7π/6 and x=2π-π/6=11π/6

x=7π/6+2nπ and x=11π/6+2nπ

now why does the first problem uses π as oppose to 2π I don't know what i'm suppose to subtract/add to in order to have the solution. When i do the homework it's always the other and i don't understand why. Am i suppose to use the angle, π, or 2π? The first problem uses it's angle and π - it's angle while the second problem uses π + its angle and 2π - it's angle to get a solution.