Question

if you are given the hypotenuse and an adjacent side, which trig function should you use?
cosine
tangent
sine

Explanation:

Step1: Recall trigonometric function definitions

$$\sin\theta=\frac{\text{opposite}}{\text{hypotenuse}},\quad\cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}},\quad\tan\theta=\frac{\text{opposite}}{\text{adjacent}}$$

Step2: Match given sides with functions

Given hypotenuse and adjacent side. From $\cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}}$, cosine function is used.

Answer:

cosine