Chapter 7: Problem 19
Set up the integral to compute the arc length of the function on the given interval. Do not evaluate the integral. \(f(x)=\frac{1}{x}\) on [1,2]
Short Answer
Expert verified
The integral for the arc length is \( \int_{1}^{2} \sqrt{1 + \frac{1}{x^4}} \, dx \).
Step by step solution
01
Identify the Formula for Arc Length
To find the arc length of a function \( y = f(x) \) from \( x = a \) to \( x = b \), we use the formula for arc length: \[ L = \int_{a}^{b} \sqrt{1 + \left( \frac{dy}{dx} \right)^2} \, dx \]
02
Differentiate the Function
Find the derivative of the function \( f(x) = \frac{1}{x} \). The derivative is \( f'(x) = -\frac{1}{x^2} \).
03
Square the Derivative
Square the derivative found in the previous step: \[ \left( \frac{dy}{dx} \right)^2 = \left( -\frac{1}{x^2} \right)^2 = \frac{1}{x^4} \]
04
Compute the Expression Inside the Square Root
Add 1 to the squared derivative: \[ 1 + \left( \frac{dy}{dx} \right)^2 = 1 + \frac{1}{x^4} \]
05
Set Up the Integral for Arc Length
Substitute the expression into the arc length formula: \[ L = \int_{1}^{2} \sqrt{1 + \frac{1}{x^4}} \, dx \] This integral represents the arc length of the function over the interval [1, 2].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integral
A definite integral represents the accumulation of quantities, which can be interpreted as the total "area" under a curve within a specified interval \( [a, b] \). Unlike an indefinite integral, which represents a family of functions and includes a constant of integration (\"C\"), the definite integral computes a numerical value for this total area.
- Notation: A definite integral is noted \( \int_{a}^{b} f(x) \, dx \), where \( f(x) \) is the function being integrated over the interval \( [a, b] \).
- Evaluation: It requires finding the antiderivative of \( f(x) \), then applying the "Fundamental Theorem of Calculus," which involves evaluating this antiderivative at the upper limit \( b \) and lower limit \( a \), and finding their difference. \[ F(b) - F(a) \]
- Application: In the context of arc length, the definite integral helps us sum up the tiny line segments making up the curve from \( x = a \) to \( x = b \), giving us the total arc length.
Derivatives
A derivative represents the rate at which a function changes at any given point. When we find the derivative of a function, we're essentially determining the slope or steepness of its curve at a specific point.
- Definition: Mathematically, the derivative of a function \( f(x) \) is defined as: \[ f'(x) = \lim_{h \to 0} \frac{f(x+h)-f(x)}{h} \]
- Notation: It can be denoted as \( f'(x) \), \( \frac{dy}{dx} \), or \( \frac{df}{dx} \), among others.
- Purpose: Derivatives are used to find rates of change, tangents to curves, and optimizations among other things.
Differentiation
Differentiation is the process of finding a derivative, which provides critical insights into the behavior of functions. The rules and techniques for differentiation allow us to find derivatives systematically.
- Basic Rule: The power rule is often used and states that for any function \( x^n \), the derivative is \( nx^{n-1} \).
- Chain Rule: Necessary for composite functions \( f(g(x)) \), it states \( (f(g(x)))' = f'(g(x)) \cdot g'(x) \).
- Product and Quotient Rules: These apply when differentiating functions that are multiplied together or divided. The quotient rule is used for \( \frac{u}{v} \) and is \( (\frac{u}{v})' = \frac{u'v - uv'}{v^2} \).