Chapter 2: Problem 96
True or False? In Exercises \(93-96\) , determine whether the statement is true or false. If it is false, explain why or give an example that shows it is false. If a function is differentiable at a point, then it is continuous at that point.
Short Answer
Expert verified
The statement 'If a function is differentiable at a point, then it is continuous at that point' is true.
Step by step solution
01
Understanding Differentiability and Continuity
Differentiability at a point means that a function has a derivative at that point, or that the slope of the function is defined there. Continuity at a point, on the other hand, means that there are no jumps, breaks or holes at that point in the function. The function doesn’t skip any value on the y-axis around this point.
02
Relating Differentiability to Continuity
By definition, if a function \(f(x)\) is differentiable at \(x = c\), then the limit of the difference quotient exists at \(x = c\), i.e., \[\lim_{h \to 0} \frac{f(c+h) - f(c)}{h}\] exists. This means that the function is smooth, without any breaks, at \(x = c\). Thus, if a function is differentiable at a point, then it is continuous at that point.
03
Verification
Also, it is known, if a function is differentiable at a point, it will be continuous at that point. This can be verified by the fact that every differentiable function is continuous. Although the converse is not true; a function could be continuous at a point without being differentiable there.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Continuity
Continuity is a fundamental property of functions in calculus. We say a function is continuous at a point if it has no sudden jumps, breaks, or holes at that point. Imagine a smooth, unbroken line drawn on a graph, without lifting the pencil. If a function can be represented like this around a certain point, we consider it continuous at that point. This implies that there's no abrupt change in values. Mathematically, a function \( f(x) \) is continuous at \( x = c \) if the following conditions are met:
- The function \( f(x) \) is defined at \( x = c \).
- The limit \( \lim_{x \to c} f(x) \) exists.
- The limit of the function as it approaches \( c \) is equal to the function value, \( \lim_{x \to c} f(x) = f(c) \).
Derivative
The derivative provides information about the rate of change of a function. It can be thought of as the slope of the tangent line to the curve of the function at a given point. When we say that a function is differentiable at a point, it means the derivative exists at that particular point, offering insight into how the function behaves locally. To find a derivative at \( x = c \), we substitute into the formula: \[ f'(c) = \lim_{h \to 0} \frac{f(c+h) - f(c)}{h} \]This formula calculates the slope of the tangent line at \( c \), illustrating how the function changes instantaneously.It's important to note:
- If a function is differentiable at a point, it must be continuous at that point. This is because differentiability implies smoothness.
- The reverse is not always true; a function may be continuous but not differentiable (like a sharp corner or cusp).
Limit
Limits are crucial in understanding the behavior of functions as they approach a certain point. The concept of a limit helps in examining what happens to function values as the input gets closer to a certain value, without necessarily reaching it. A simple example would be looking at \( \lim_{x \to c} f(x) \), where you study how \( f(x) \) behaves as \( x \) approaches \( c \). This is foundational for concepts like continuity and differentiability.Here's what you need to grasp about limits:
- A limit exists if the function approaches a specific value, ensuring no sudden jumps or inconsistent behavior at the edge.
- The process of taking limits is used in defining both derivatives and integrals.
Difference Quotient
The difference quotient is a crucial expression used in calculus to find the derivative of a function. It forms the backbone for comprehending how functions change at an exact point. You can think of it as a way to approximate the slope of the secant line between two points on the function.For any function \( f(x) \), the difference quotient is given by: \[ \frac{f(c+h) - f(c)}{h} \]where \( h \) represents a small increment from \( c \). When \( h \) approaches 0, the difference quotient transforms into the derivative.Key points about the difference quotient:
- It's essential in the formal definition of a derivative.
- It provides a means to visualize and calculate the function's rate of change.
- The limit of the difference quotient as \( h \to 0 \) gives the exact slope of the tangent line at that point.