use the half angle formulas to find the exact value of cos 11pi/12 (hinting that 11pi/12=11pi/6/2)

Answer 1

Cos(11π/12) = -0.965925 x 180/π = -55.343°

Using Cos(Θ/2) = ±√( [1 + Cos(Θ)] / 2 )

Cos([11π/6)]/2) = -0.965925 x 180/π = -55.343°

Answer 2

cos(11π/12) = - cos(π/12) = - sqrt((1+ cos(π/6))/2) = - (1 + sqrt(3))/2)^1/2 = - (2 + (3)^1/2)^1/2/2