Final answer:
The value of θ that makes the statement true is 120° or 240°.
Step-by-step explanation:
To find the value of θ that makes the statement true, we need to solve the equation cos(θ) = sin(-30°).
To do this, we can use the fact that sin(-θ) = -sin(θ) and evaluate sin(-30°) = -sin(30°). Since sin(30°) = 1/2, we have -sin(30°) = -1/2.
Therefore, cos(θ) = -1/2, and by inspecting the unit circle or using inverse cosine function, we can find that θ = 120° or θ = 240°.