Final answer:
In mathematics, lines extending from the horizontal axis across a chart are called gridlines or tick marks and help read data points against the axes. The horizontal axis often represents the independent variable in a graph, and line graphs show the relationship between two variables through a series of connected data points.
Step-by-step explanation:
In the context of mathematics, particularly when discussing graphing, lines extending from the horizontal or vertical axes across the plot area of a chart are typically referred to as gridlines or tick marks. These lines aid in the visualization of data points on the chart, making it easier to determine their precise values against the axes. Line graphs represent a relationship between two variables: one measured on the horizontal axis, often called the independent variable or the x-axis, and the other measured on the vertical axis, known as the dependent variable or the y-axis. The equation of a straight-line graph can typically be expressed in the form y = mx + b, where m represents the slope of the line and b represents the y-intercept.
For example, consider a line graph showing the relationship between the amount of time spent studying (measured on the horizontal axis) and the score on a test (measured on the vertical axis). The points on the graph represent the frequency of test scores corresponding to various amounts of study time, and these points are connected by line segments to illustrate trends in the data.