Verified answer

cos(π/2+θ)= cos(π/2)*cosθ -sin(π/2)*sinθ =

cos(π/2) =0

sin(π/2)=1

cos(π/2)*cosθ -sin(π/2)*sinθ = 0*cosθ -1*sinθ =-sinθ

cos(pi/2 + theta) = cos(pi/2)*costheta - sin(pi/2)* sin theta

= 0 -1*sin theta = -sin theta