Answer: The answer is cosine of that acute angle.
Step-by-step explanation: We are to find the ratio of the adjacent side of an acute angle to the hypotenuse.
In the attached figure, we draw a right-angled triangle ABC, where ∠ABC is a right angle, and ∠ACB is an acute angle.
Now, side adjacent to ∠ACB is BC, which is the base with respect to this particular angle, and AC is the hypotenuse.
Now, the ratio is given by
Thus, the ratio is cosine of the acute angle.
