Course: Calculus I
Topic: Limits and Continuity
Subtopic: Limits at Infinity


A limit at infinity means a limit whose x-value is approaching positive or negative infinity. Graphically these limits explore the function as x grows infinitely large or infinitely small. If the limit exists it shows the function has a horizontal asymptote line at that limiting value. Limits at infinity can also be used to find an oblique asymptote line (or asymptote curve).

When evaluating a limit at infinity a trick that is sometimes useful is to force the variable into denominators of fractions that would then be made negligible (thus approach zero) as the variable approaches infinity. An example will be presented in class.


By the end of this topic you should know and be prepared to be tested on:


Terms you should be able to define: horizontal asymptote line, oblique (slant) asymptote, limit at infinity, approaching infinity (in terms of limits)

Mini-Lectures and Examples

STUDY: Infinite Limits & Limits at Infinity & Limits Electronically

Supplementary Resources (optional)

Video: Limits at Infinity and Horizontal Asymptotes, Selwyn Hollis's Video Calculus

Lesson: Asymptotic Behavior of Functions, Dale Hoffman's Contemporary Calculus

rev. 2020-10-10