Making sense of continuity at a point where f(x) = Infinity?

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SUMMARY

The discussion centers on the concept of continuity for functions where f(x_0) = ∞. It establishes that the standard definition of continuity fails because it requires |f(x_0) - f(x)| < ε, which is impossible when f(x_0) is infinite. The participants explore alternative approaches, such as considering the reciprocal of the function, 1/f(x_0) = 0, to redefine continuity in this context. This leads to the formulation of the condition |1/f(x_0) - 1/f(x)| < ε as a potential way to analyze continuity at points of infinity.

PREREQUISITES
  • Understanding of the standard definition of continuity in real analysis.
  • Familiarity with the concept of limits and the extended real number system.
  • Knowledge of reciprocal functions and their properties.
  • Basic grasp of ε-δ definitions in calculus.
NEXT STEPS
  • Research the properties of extended real-valued functions.
  • Study the implications of continuity at infinity in real analysis.
  • Learn about the ε-δ definition of continuity and its applications.
  • Explore the concept of limits involving infinity and their graphical interpretations.
USEFUL FOR

Mathematicians, students of calculus and real analysis, and anyone interested in advanced concepts of continuity and limits in mathematical functions.

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Is there a way to make sense of the following statement: "[itex]f[/itex] is continuous at a point [itex]x_0[/itex] such that [itex]f(x_0) = \infty[/itex]?" The standard definition of continuity seems to break down here: For any [itex]\epsilon > 0[/itex], there is no way to make [itex]|f(x_0) - f(x)| < \epsilon[/itex], since this is equivalent to making [itex]|\infty - f(x)| < \epsilon[/itex], which cannot happen, since [itex]\infty - y = \infty[/itex] for every [itex]y\in \mathbb R[/itex] and [itex]\infty - \infty[/itex] is undefined. So is there any way to make sense of continuity of an extended real-valued function at a point where it's infinite?
 
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Could you try regarding [itex]f(x_0) = \infty[/itex] as [itex]1/f(x_0) = 0[/itex], and so make

[tex]\left|\frac{1}{f(x_0)}-\frac{1}{f(x)} \right| < \epsilon[/tex]
?
 

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