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Ch. 6 - Applications of Integration
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 6, Problem 6.5.14

9–20. Arc length calculations Find the arc length of the following curves on the given interval.
y = x^3/2 / 3 − x^1/2 on [4, 16]

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1
Identify the function given: \(y = \frac{x^{3/2}}{3} - x^{1/2}\), and the interval \([4, 16]\) over which we want to find the arc length.
Recall the formula for the arc length of a curve \(y = f(x)\) from \(x = a\) to \(x = b\): \(L = \int_a^b \sqrt{1 + \left(\frac{dy}{dx}\right)^2} \, dx\)
Find the derivative \(\frac{dy}{dx}\) of the function: First, rewrite the function as \(y = \frac{1}{3} x^{3/2} - x^{1/2}\). Then differentiate term-by-term using the power rule.
Square the derivative \(\left(\frac{dy}{dx}\right)^2\) and add 1 inside the square root to form the integrand: \(\sqrt{1 + \left(\frac{dy}{dx}\right)^2}\)
Set up the definite integral for the arc length over the interval \([4, 16]\): \(L = \int_4^{16} \sqrt{1 + \left(\frac{dy}{dx}\right)^2} \, dx\). Evaluate this integral to find the arc length.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Arc Length Formula

The arc length of a curve y = f(x) from x = a to x = b is found using the integral L = ∫_a^b √(1 + (dy/dx)^2) dx. This formula sums the lengths of infinitesimal line segments along the curve, providing the total distance traveled along it.
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Arc Length of Parametric Curves

Derivative of the Function

To apply the arc length formula, you must compute the derivative dy/dx of the given function y = (x^(3/2))/3 − x^(1/2). This involves using power rule differentiation for fractional exponents to find the slope of the curve at any point.
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Derivatives of Other Trig Functions

Definite Integration

After finding the integrand √(1 + (dy/dx)^2), evaluate the definite integral from x = 4 to x = 16. This requires integrating the expression over the interval to obtain the exact arc length, often involving substitution or numerical methods if the integral is complex.
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Definition of the Definite Integral