6. sin(π2+θ)+cos(π2−θ)=55\sin\left(\frac\pi2+\theta\right)+\cos\left(\frac\pi2-\theta\right)=\frac{\sqrt5}{5}sin(2π+θ)+cos(2π−θ)=55일 때, sinθcosθ\sin\theta\cos\thetasinθcosθ의 값은? [3점]