
Advanced Engineering Mathematics
10th Edition
ISBN: 9780470458365
Author: Erwin Kreyszig
Publisher: Wiley, John & Sons, Incorporated
expand_more
expand_more
format_list_bulleted
Concept explainers
Question
![Consider the function \( f : \mathbb{R} \to \mathbb{R} \) given piecewise by
\[
f(x) =
\begin{cases}
1 & \text{if } x \text{ is irrational} \\
0 & \text{if } x \text{ is rational}
\end{cases}
\]
Now let \( c \) be any real number in \( \mathbb{R} \).
**Case 1:** If \( c \) is rational, choose a sequence \( (x_n : n \in \mathbb{N}) \) of irrational numbers converging to \( c \) (which is allowed by Proposition 4.6.1). So \( x_n \to c, f(x_n) = 1 \) for all \( n \), and \( f(c) = 0 \). But since \( f(x_n) = 1 \) for all \( n \), we cannot have \( f(x_n) \to 0 \) (a sequence of 1's cannot converge to 0!). That is, it is impossible that \( f(x_n) \to f(c) \), so by Theorem 4.6.7, \( f \) cannot be continuous at \( c \).
**What is Case 2?**](https://content.bartleby.com/qna-images/question/45ccc3c2-853e-4ee6-91f9-7e4723419012/95ef05f1-4f95-41ec-b5ae-d9e00c7b36fc/qph12x6_thumbnail.png)
Transcribed Image Text:Consider the function \( f : \mathbb{R} \to \mathbb{R} \) given piecewise by
\[
f(x) =
\begin{cases}
1 & \text{if } x \text{ is irrational} \\
0 & \text{if } x \text{ is rational}
\end{cases}
\]
Now let \( c \) be any real number in \( \mathbb{R} \).
**Case 1:** If \( c \) is rational, choose a sequence \( (x_n : n \in \mathbb{N}) \) of irrational numbers converging to \( c \) (which is allowed by Proposition 4.6.1). So \( x_n \to c, f(x_n) = 1 \) for all \( n \), and \( f(c) = 0 \). But since \( f(x_n) = 1 \) for all \( n \), we cannot have \( f(x_n) \to 0 \) (a sequence of 1's cannot converge to 0!). That is, it is impossible that \( f(x_n) \to f(c) \), so by Theorem 4.6.7, \( f \) cannot be continuous at \( c \).
**What is Case 2?**
Expert Solution

This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
This is a popular solution
Trending nowThis is a popular solution!
Step by stepSolved in 2 steps with 1 images

Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, advanced-math and related others by exploring similar questions and additional content below.Similar questions
- -3 18 < X < 16 14 12 10 8 -2 -1 For the above rational function f( x ) = 6 4 2 1 2 30 18 4x² + 1 " identify the interval on which f is concave down.arrow_forwardExpress the rational function as a sum or difference of two simpler rational expressions. ess 3x2 3x2 (x-1)(x + x + 1) 193. x' - 1arrow_forward
Recommended textbooks for you
- Advanced Engineering MathematicsAdvanced MathISBN:9780470458365Author:Erwin KreyszigPublisher:Wiley, John & Sons, IncorporatedNumerical Methods for EngineersAdvanced MathISBN:9780073397924Author:Steven C. Chapra Dr., Raymond P. CanalePublisher:McGraw-Hill EducationIntroductory Mathematics for Engineering Applicat...Advanced MathISBN:9781118141809Author:Nathan KlingbeilPublisher:WILEY
- Mathematics For Machine TechnologyAdvanced MathISBN:9781337798310Author:Peterson, John.Publisher:Cengage Learning,

Advanced Engineering Mathematics
Advanced Math
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Wiley, John & Sons, Incorporated

Numerical Methods for Engineers
Advanced Math
ISBN:9780073397924
Author:Steven C. Chapra Dr., Raymond P. Canale
Publisher:McGraw-Hill Education

Introductory Mathematics for Engineering Applicat...
Advanced Math
ISBN:9781118141809
Author:Nathan Klingbeil
Publisher:WILEY

Mathematics For Machine Technology
Advanced Math
ISBN:9781337798310
Author:Peterson, John.
Publisher:Cengage Learning,

