Skip to main content
Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.7.36

[Technology Exercise] When solving Exercises 33-40, you may need to use a calculator or a computer.
Find, to two decimal places, the areas of the surfaces generated by revolving the curves in Exercises 35 and 36 about the x-axis.
y = x²/4, 0 ≤ x ≤ 2

Guida verificata passo dopo passo
1
Identify the formula for the surface area of a solid of revolution about the x-axis: \[ S = \int_a^b 2\pi y \sqrt{1 + \left(\frac{dy}{dx}\right)^2} \, dx \]
Given the curve \[ y = \frac{x^2}{4} \], find its derivative with respect to \[ x \]: \[ \frac{dy}{dx} = \frac{d}{dx} \left( \frac{x^2}{4} \right) = \frac{x}{2} \]
Substitute \[ y \] and \[ \frac{dy}{dx} \] into the surface area formula: \[ S = \int_0^2 2\pi \left( \frac{x^2}{4} \right) \sqrt{1 + \left( \frac{x}{2} \right)^2} \, dx \]
Simplify the expression inside the square root and the integrand: \[ S = \int_0^2 2\pi \frac{x^2}{4} \sqrt{1 + \frac{x^2}{4}} \, dx = \int_0^2 \frac{\pi x^2}{2} \sqrt{1 + \frac{x^2}{4}} \, dx \]
Evaluate the integral using an appropriate method (such as substitution or numerical integration) to find the surface area, then round the result to two decimal places.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
6m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Surface Area of Revolution

The surface area of a solid formed by revolving a curve around an axis is found using an integral formula. For revolution about the x-axis, the formula involves integrating 2π times the radius (the y-value) times the arc length element. This concept connects geometry with calculus to measure curved surfaces.
Video consigliato:
09:07
Example 1: Minimizing Surface Area

Arc Length Element (ds)

The arc length element ds represents a small segment of the curve and is given by √(1 + (dy/dx)²) dx. It accounts for the curve's slope, ensuring the surface area calculation accurately follows the curve's shape rather than just the x-interval.
Video consigliato:
Percorso guidato
06:29
Arc Length of Parametric Curves

Definite Integration with Limits

Definite integration calculates the exact accumulated value over an interval, here from x = 0 to x = 2. Applying limits ensures the surface area corresponds precisely to the specified portion of the curve, providing a numerical result to two decimal places.
Video consigliato:
Percorso guidato
05:43
Definition of the Definite Integral