In the rectangular coordinate system, the vertical number line is referred to as the y-axis. This axis represents the vertical component of any point in a two-dimensional space, where every point has an x-coordinate and a y-coordinate. The y-axis runs vertically and typically intersects with the horizontal number line, known as the x-axis, at the origin point (0,0).
The y-axis is essential for plotting points on a graph, helping to visualize relationships between variables. Each point on the y-axis corresponds to a specific value of the dependent variable, often represented as y in equations and graphs. Understanding the role of the y-axis is crucial for analyzing linear equations, functions, and various mathematical concepts in coordinate geometry.
In summary, the vertical number line in the rectangular coordinate system is known as the y-axis, and it plays a vital role in graphing and understanding mathematical relationships.