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: 40

Answer

$$L = \int_{0}^{1} \sqrt{2 + \frac 1 {2t}} \space dt \approx 2.0915$$

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 $\frac{dy}{dt}$ $\frac{dx}{dt} = \frac{d(t + \sqrt t)}{dt} = 1 + \frac{1}{2 \sqrt t}$ $\frac{dy}{dt} = \frac{d(t - \sqrt t)}{dt} = 1 - \frac{1}{2 \sqrt t}$ 3. Substitute the values into the definite integral: $L = \int_{0}^{1} \sqrt{(1 + \frac{1}{2 \sqrt t})^2 + (1 - \frac{1}{2 \sqrt t})^2} \space dt$ $L = \int_{0}^{1} \sqrt{(1 + 2(\frac{1}{2 \sqrt t})+ \frac 1 {4t}) + (1 - 2(\frac{1}{2 \sqrt t})+ \frac 1 {4t})} \space dt$ $L = \int_{0}^{1} \sqrt{(1 + \frac 1 {4t}) + (1 + \frac 1 {4t})} \space dt$ $L = \int_{0}^{1} \sqrt{2 + \frac 2 {4t}} \space dt$ $L = \int_{0}^{1} \sqrt{2 + \frac 1 {2t}} \space dt$ 4. Write this integral on your calculator (you can use online integral calculators), and get the result. $L \approx 2.0915$
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