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Mathematics · Ch 17 — Continuity

Infinite Discontinuity

17.1.9

Infinite Discontinuity

A third, more dramatic way a function can fail to be continuous is by growing without any bound at all as xx approaches the point — there is then no finite height the graph is settling towards, from one side or both. This is called an infinite discontinuity:

A function f(x) is said to have an infinite discontinuity at x=a if lim⁡x→a−f(x)=±∞ or lim⁡x→a+f(x)=±∞.\textbf{A function } f(x) \textbf{ is said to have an infinite discontinuity at } x=a \textbf{ if } \lim_{x\to a^-} f(x)=\pm\infty \textbf{ or } \lim_{x\to a^+} f(x)=\pm\infty. …

Figure 8.7Fig. 8.7 – the graph of y = 1/x near x = 0

What this figure shows. Two separate branches of a hyperbola: for x>0x>0 the curve starts very high near the Y-axis and falls towards the X-axis as xx increases, while for x<0x<0 the mirror-image branch starts very low near the Y-axis and rises towards the X-axis as xx decreases further negative – both branches hug the vertical line x=0x=0 without ever touching it, showing the function racing off to +∞+\infty on one side an …