Multivariable Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 0-53849-787-4
ISBN 13: 978-0-53849-787-9

Chapter 10 - Parametric Equations and Polar Coordinates - 10.2 Exercises - Page 676: 38

Answer

$$L = \int_{1}^{4} \sqrt{(16t^6 + 4t^2 -4t + 1 )} \space dt \approx 255.3756$$

Work Step by Step

1. Write the formula for the length "$L$"of a curve: $$L = \int_{\alpha}^{\beta} \sqrt{(\frac{dx}{dt})^2 + (\frac{dy}{dt})^2} \space dt$$ 2. Find $\frac{dx}{dt}$ and $\frac{dy}{dt}$ $\frac{dx}{dt} = \frac{d(t^2 - t)}{dt} = 2t -1$ $\frac{dy}{dt} = \frac{d(t^4)}{dt} = 4t^3$ 3. Substitute the values into the definite integral: $L = \int_{\alpha}^{\beta} \sqrt{(2t -1)^2 + (4t^3)^2} \space dt$ $L = \int_{\alpha}^{\beta} \sqrt{(4t^2 -4t + 1) + (16t^6)} \space dt$ $L = \int_{\alpha}^{\beta} \sqrt{(16t^6 + 4t^2 -4t + 1 )} \space dt$ - Since $t$ goes from 1 to 4: $L = \int_{1}^{4} \sqrt{(16t^6 + 4t^2 -4t + 1 )} \space dt$ 4. Write this integral on your calculator, and get the result. $L \approx 255.3756$
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