Infinite Limits & Vertical Asymptotes

1. Infinite Limits & Vertical Asymptotes Section 1.5

2. After this lesson, you will be able to: • determine infinite limits from the left and from the right • find and sketch the vertical asymptotes of the graph of a function

3. ______ ______ Infinite Limits-Graphically Consider the function, _________ is not in the domain of the function. So, we are curious about what is happening to the function as x approaches 0. We’ll say that as x approaches 0 is a limit of special interest. As x approaches 0 from the right, graphically we can see that the function is going off to positive infinity… Graph the function… As x approaches 0 from the left, graphically we can see that the function is going off to negative infinity…

4. Infinite Limits-Numerically Let’s examine the table of values to reinforce our decision… Set TBL to be .01. • You can see that as x gets closer to 0 from values that are • larger than 0, the function goes off to positive infinity. (RHL) • smaller than 0, the function goes off to negative infinity. (LHL)

5. Infinite Limits Eventually, we should be able to find the limit as x approaches 0 without using a table or a graph of the function, First, let’s consider what happens as x approaches 0 from the right (values larger than 0). Evaluate by hand: We say that the graph _______________ _______________ ___________ as x approaches 0 from the right.

6. Infinite Limits Next, let’s consider what happens as x approaches 0 from the left (values smaller than 0). Evaluate by hand: We say that the graph _______________ _______________ ___________ as x approaches 0 from the left.

7. Infinite Limits You probably won’t see this definition in the textbook. 

8. Infinite Limits No matter how we evaluate the limit (graphically, numerically, or analytically), we know that

9. x = c Infinite Limits the line x = c is a vertical asymptote to the graph. In general, if the limit of a function as x approaches a number from the left OR from the right decreases/increases without bound, then the line x = c is a vertical asymptote to the graph.

10. Left limit 1 Right limit Finding Limits of Special Interest Example*: Find the limits of special interest for the function, What’s the domain of f? _______________ Since 1 is NOT in the domain, we are interested in what is happening to the function near x = 1…this creates two limits of special interest…the right-hand limit at x = 1 and the left-hand limit at x = 1.

11. Limits of Special Interest From our limit results, we can conclude that the function has a vertical asymptote at x = 1.

12. Trig Example* Find the vertical asymptotes of the function, 1) Define the function in terms of sine and cosine. 2) Determine the domain. 3) Write the equation(s) of the vertical asymptotes. 4) Graph on your calculator to reinforce your result.

13. Example 1 Determine the vertical asymptotes of the graph.

14. Example 2 Use limits to determine any vertical asymptotes of the graph.

15. Example 3 Use limits to determine any vertical asymptotes of the graph.

16. Properties of Infinite Limits Let c and L be real numbers, let f and g be functions such that and . 1. **Similar properties would hold if

17. Examples of Properties of Infinite Limits

18. Homework Section 1.5: page 88 #1-23 odd, 29-45 odd, 49, 51