Mathematics

This is about identifying which side ratio gives you the cosine of an angle in a right triangle. Remember that $\cos\theta$ always equals the ratio of the adjacent side to the hypotenuse — the key is figuring out which side is which from angle $A$'s perspective. Since $\angle B$ is the right angle, $AC$ must be the hypotenuse, and you need to identify which of the two remaining sides touches angle $A$.

This is about identifying which side ratio gives you the cosine of an angle in a right triangle. Remember that $\cos\theta$ always equals the ratio of the adjacent side to the hypotenuse — the key is figuring out which side is which from angle $A$'s perspective. Since $\angle B$ is the right angle, $AC$ must be the hypotenuse, and you need to identify which of the two remaining sides touches angle $A$.