f(-π/6)=√2cos(-π/6-π/ 12)= 1
∫cosθ= 3/5，θ∈(3π/2，2π)
∴sinθ=-4/5
f(2θ+π/3)=√2 cos(2θ+π/3-π/ 12)=√2 cos(2θ+π/4)=√2[cos(2θ)*√2/2-sin(2θ)*√2/2]
=cos(2θ)-sin(2θ)=2(cosθ)^2- 1-2sinθcosθ
=2*9/25- 1+2*3/5*4/5
= 17/25