Aratio is a rate sometimes, always, or never true ?

The question is asking to state or choose among the following choices that tells about the ratio's rate and base on my research, It will always be true because it has exact value and not just a mere guess but factual ratio. I hope you are satisfied with my answer and feel free to ask for more 

Hello! i hope this
since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.