1) sin (17π/6) = sin (12π + 5π) = sin(2π + 5π) = sin 5π =
6 6 6 6
= sin(π - π) = sin (π/6) = 1/2
6
2) cos(-55π/6) = cos(55π/6) = cos (60π - 5π) = cos(10π - 5π) =
6 6 6
= cos (2π*5 - 5π) = cos 5π = cos (π - π) = -cos (π/6) = -√3
6 6 6 2
3) 1 - √3 = 1-√3
2 2 2