One thing I learned was how to distinguish the different ratios using the acronym “SOHCAHTOA”.

the acronym stands for “sin opposite hypotenuse, cosine adjacent hypotenuse, tangent opposite adjacent”.

you can implement it in a question like this for example, you can see that the side are labeled and we units on the hypotenuse side and the adjacent side, but we don’t have anything on the opposite side so we know the ration cant include an opposite side on it. when we look at “SOHCAHTOA” to see which ratio we will be using, we can take off the ratios that have an opposite side in it so, that removes both Sin and Tangent, which leaves us with Cosine to finish our question with.