find the reference angle

Question

Without using a calculator, compute the sine and cosine of  by using the reference angle.What is the reference angle?     radians.In what quadrant is this angle?  (answer 1, 2, 3, or 4)         

(Type sqrt(2) for  and sqrt(3) for .)

Answer 1

θ = 7π/6 then reference angle θ' = 7π/6 - π = π/6 (quadrant III)

sin(7π/6) = - sin(π/6) = - 1/2.

cos(7π/6) = - cos(π/6) = - √3/2

Answer 2

sin7pi/6 = sin(-pi/6) = sin(-30) = -1/2

cos7pi/6 =cos(-pi/6) = -cos30 = -(1/2)sqr3