θ approaches π/2
numerator = (1 - sin(θ))
denominator = (1 + cos(6θ))
lim (θ -> π/2) (1 - sin(θ)) / (1 + cos(6θ)) (L'Hospital's)
= lim (θ -> π/2) -cos(θ) / -6sin(6θ)
= -cos(π/2) / -6sin(6 x π/2)
= 0 / 0 (denominator = (1 + cos(6θ)))
= lim (θ -> π/2) sin(θ) / 36cos(6θ)
= sin(π/2) / 36cos(6 x π/2)
= 1/-36
limit (θ -> π/2) [(1 - sin(θ)) / (1 + cos(6θ))] = -1/36