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Example: Reading Function Values, Intercepts, Domain, and Range from a Graph

By analyzing the visual graph of a mathematical function, various properties can be deduced directly from its plotted coordinate points. Consider a periodic wavy graph extending infinitely in both directions along the horizontal xx-axis. Because the curve has a corresponding point for all real xx-values, its domain is physically represented as the interval (,)(-\infty, \infty). Vertically, the function's plotted yy-values strictly oscillate between a minimum of 1-1 and a maximum of 11, making the corresponding range [1,1][-1, 1]. To evaluate specific function values, one must match the given xx-input with the precise yy-output on the curve. For instance, to evaluate f\left(\frac{3}{2}\pi ight), locate 32π\frac{3}{2}\pi on the xx-axis and read the correlating yy-coordinate of the graph, which is 1-1; thus, f\left(\frac{3}{2}\pi ight) = -1. Furthermore, to find the xx-values where f(x)=0f(x) = 0, identify the xx-intercepts where the graph crosses the horizontal axis. For this specific graph, the intercepts appear at points such as (2π,0)(-2\pi, 0), (π,0)(-\pi, 0), (0,0)(0, 0), (π,0)(\pi, 0), and (2π,0)(2\pi, 0), concluding that the solutions are 2π-2\pi, π-\pi, 00, π\pi, and 2π2\pi. By inspecting the vertical intersection, the single yy-intercept occurs where the graph crosses the yy-axis when x=0x = 0, which happens precisely at the origin (0,0)(0, 0).

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Updated 2026-04-24

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Ch.3 Graphs and Functions - Intermediate Algebra @ OpenStax

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