Short Answer 
The cosine function (cos(θ)) is the ratio of the adjacent side to the hypotenuse in a right triangle and corresponds to the x-coordinate on the unit circle. Given points (3, 0) and (-x, y), the relationship is established as cos(θ) = -x/3, showing how the x-value relates to the cosine of angle θ.
Step 1: Understanding the Cosine Function
The cosine function, denoted as cos(θ), represents the ratio of the adjacent side to the hypotenuse in a right triangle. On the unit circle, it is also defined as the x-coordinate of the point that corresponds to the angle θ. In this case, it helps illustrate the relationship between the angle and the coordinates in two-dimensional space.
Step 2: Analyzing Given Parameters
In this context, we are given specific parameters to analyze the cosine function. The coordinates provided, specifically the points (3, 0) and (-x, y), can be used to understand how cos(θ) relates to these coordinates. By determining the x-values, one can directly compute the cosine value based on the geometric interpretation within the unit circle.
Step 3: Establishing the Relation
Using the relationships derived from the unit circle and the provided parameters, we conclude that the statement cos(θ) = -x/3 is accurate. This equation indicates how the x-coordinate (in terms of x) correlates with the cosine value of the angle θ. Therefore, it highlights the essential relationship between angles and their respective cosines in a trigonometric context.