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(a) Show that the absolute value function $ F(x) = | x | $ is continuous everywhere.(b) Prove that if $ f $ is a continuous function on an interval, then so is $ | f | $.(c) Is the converse of the statement in part (b) also true? In other words, if $ | f | $ is continuous, does it follow that $ f $ is continuous? If so, prove it. If not, find a counterexample.

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04:55

Daniel Jaimes

Calculus 1 / AB

Chapter 2

Limits and Derivatives

Section 5

Continuity

Limits

Derivatives

Missouri State University

Campbell University

University of Nottingham

Lectures

04:40

In mathematics, the limit of a function is the value that the function gets very close to as the input approaches some value. Thus, it is referred to as the function value or output value.

In mathematics, a derivative is a measure of how a function changes as its input changes. Loosely speaking, a derivative can be thought of as how much one quantity is changing in response to changes in some other quantity; for example, the derivative of the position of a moving object with respect to time is the object's velocity. The concept of a derivative developed as a way to measure the steepness of a curve; the concept was ultimately generalized and now "derivative" is often used to refer to the relationship between two variables, independent and dependent, and to various related notions, such as the differential.

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(a) Show that the absolute…

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Prove: If f is a continuou…

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(a) Prove that if $f$ is c…

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Prove: If $f$ is continuou…

the first problems we want to prove the absolute value function is continuous everywhere. So first, so this is the absence function. And to say we want to prove um f of X is continuous at one point say execute A. Then we can see the difference of the function. So this if you write it is actually echo to absolute value absolute value of x minus absolute value of A. And if you use a triangle inequality you can prove this is smaller, then absolutely a value of x minus A. So when X 10 to a. You'll see X -1-0. So this means because this function is the other bands with sometimes goes to Zeros and F of the x minus F. A. So this one also tends to zero. So that means the function F is continuous at two executive A. And his hair is like an arbitrary so ffx is continues everywhere. And for the second province. So we weren't proves that fs continues then similarly for absolute value of X. So this is also easy to prove, say so if we want to through F of X is continuously at X equal to a. So what we do is so the absolute value of F at X man is absolute value of a. The difference of the function difference. This is also smarter by the triangle inequality is smarter than ffx minus F. A. Since we know if is a it continues, that means This quantity 10- zero when x. 10 to a. And this tells you this time goes to there, that means fx is continuous. So for the last province that we want to know, the answer is not true. So it is forced. And we want to find a counter examples into the examples. Also you notify. So one thing you can think uh say fo Becks If you could to one. The X is The rational numbers and -1. When X is like a Nazi rational numbers. So this function clearly it's not continues because you can just and draw the figure. So there are some dots here. So this is one and also minus one and some thoughts here. This function is not continuous. Lecture once you take the absolute value of FX. So this is Echo to save one. Right? So this is a customer of functions so it is continuous. So this means we have a country example. So after value is continues and here is a constant that the the F of X is not continues. So the answer is forced.

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