suppose that sin θ = -5/13 and cos θ =12/13. find cos (-θ )

Answer 1

The fact that sin x = -5/13 is irrelevant. We know that cos x = cos (-x). So, if cos x = 12/13, then cos (-x) yields the same result. The answer is still 12/13.

Answer 2

cosine is an even function, so cos(-θ) = cosθ = 12/13