Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 5 - Applications Of The Definite Integral In Geometry, Science, And Engineering - 5.1 Area Between Two Curves - Exercises Set 5.1 - Page 354: 29

Answer

$\text{(a)}$ \begin{align} A = \frac{4}{3} \end{align} $\text{(b)}$ \begin{align} y = 0.413x \end{align}

Work Step by Step

$\text{(a) First, we have to find the intersection:}$ \begin{align} & 2x-x^2 = 0 \\ & x = 0 \ and \ x = 2 \\ & A = \int_0^2 (2x-x^2) \ dx = \left[ x^2-\frac{x^3}{3}\right]_0^2 = \frac{4}{3} \end{align} $\text{(b) The half of the area in part (a) is $\frac{2}{3}$.}$ $\text{The intersection between y = mx and y = 2x - x$^2$:}$ \begin{align} & 2x-x^2 = mx \\ & x = 0 \ and \ x = 2-m \\ & \int_0^{2-m} mx \ dx + \int_{2-m}^2 (2x-x^2) \ dx = \left[m\frac{x^2}{2} \right]_0^{2-m} + \left[x^2 -\frac{x^3}{3}\right]_{2-m}^{2} = \\ & = m\frac{4-4m+m^2}{2} -m^2+4m - \frac{m^3-6m^2+12m}{3} = 2m-m^2+\frac{m^3}{6} = \frac{2}{3} \\ & \Rrightarrow m^3-6m^2+12m-4=0 \Rrightarrow m = 0.413 \end{align} $\text{Thus, the line that divides the area in two parts is y = 0.413x}$
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