Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.7 - Modeling with Equations - 1.7 Exercises - Page 80: 90

Answer

The length of the circle is $\approx169.1$ The length of the square is $\approx190.9$

Work Step by Step

Let's say that the part of wire used to form circle is $x$, then the second part used for square will be $y$ ($x+y=360$). Let $a$ be side of the square and $r$ radius of the circle. Area of circle is: $\pi r^2$ Area of square is: $a^2$ According to the problem, we know that the areas equal to each other. $a^2=\pi r^2$ $a=\sqrt{\pi r^2}$ (We don't consider negative option, since the length cannot be a negative number) $x=2\pi r$ $y=4a$ $4a+2\pi r = 360$ $4\sqrt{\pi r^2} + 2\pi r = 360$ $4r\sqrt\pi+2\pi r = 360$ $r(2\sqrt\pi+\pi) = 180$ $r=\frac{180}{2\sqrt\pi+\pi}\approx26.9199$ $r\approx26.92$ Circle length = $2\pi \times 26.92 \approx 169.1$ Square length = $360-169.1=190.9$
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